10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

________________________________________________________________________________________________________

FORM 10-Q

________________________________________________________________________________________________________

ý Quarterly report pursuant to section 13 or 15(d) of the Securities Exchange Act of 1934

For the quarterly period ended March 31, 2013

OR

¨ Transition report pursuant to section 13 or 15(d) of the Securities Exchange Act of 1934

For the transition period from  to

COMMISSION FILE NUMBER 001-34653

________________________________________________________________________________________________________

First Interstate BancSystem, Inc.

(Exact name of registrant as specified in its charter)

________________________________________________________________________________________________________

Montana	81-0331430
(State or other jurisdiction of incorporation or organization)	(IRS Employer Identification No.)
401 North 31st Street, Billings, MT	59116-0918
(Address of principal executive offices)	(Zip Code)

Registrant’s telephone number, including area code: 406/255-5390

______________________________________________________________

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.     Yes  ý    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files.)     Yes  ý    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer	¨	Accelerated filer	ý
Non-accelerated filer	¨	Smaller reporting company	¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).  Yes  ¨ No  ý

Indicate the number of shares outstanding of each of the Registrant’s classes of common stock:

March 31, 2013 – Class A common stock	18,424,252
March 31, 2013 – Class B common stock	25,190,690

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES Quarterly Report on Form 10-Q Index
		Page
Part I.	Financial Information
Item 1.	Financial Statements (unaudited)
	Consolidated Balance Sheets - March 31, 2013 and December 31, 2012	3
	Consolidated Statements of Income - Three Months Ended March 31, 2013 and 2012	4
	Consolidated Statements of Comprehensive Income - Three Months Ended March 31, 2013 and 2012	5
	Consolidated Statements of Changes in Stockholders’ Equity - Three Months Ended March 31, 2013 and 2012	6
	Consolidated Statements of Cash Flows - Three Months Ended March 31, 2013 and 2012	7
	Notes to Unaudited Consolidated Financial Statements	9
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	29
Item 3.	Quantitative and Qualitative Disclosures about Market Risk	41
Item 4.	Controls and Procedures	41
Part II.	Other Information
Item 1.	Legal Proceedings	42
Item 1A .	Risk Factors	42
Item  2.	Unregistered Sales of Equity Securities and Use of Proceeds	42
Item 3.	Defaults Upon Senior Securities	42
Item 4.	Mine Safety Disclosures	42
Item 5.	Other Information	42
Item 6.	Exhibits	43
Signatures		44

2

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES CONSOLIDATED BALANCE SHEETS (In thousands, except share data) (Unaudited)
	March 31, 2013		December 31, 2012
Assets
Cash and due from banks	$	116,399	$	177,978
Federal funds sold	4,856		730
Interest bearing deposits in banks	377,288		622,624
Total cash and cash equivalents	498,543		801,332
Investment securities:
Available-for-sale	2,011,169		1,995,258
Held-to-maturity (estimated fair values of $220,115 and $218,933 at March 31, 2013 and December 31, 2012, respectively)	210,426		208,223
Total investment securities	2,221,595		2,203,481
Loans held for investment	4,169,116		4,157,470
Mortgage loans held for sale	55,443		66,442
Total loans	4,224,559		4,223,912
Less allowance for loan losses	97,904		100,511
Net loans	4,126,655		4,123,401
Premises and equipment, net of accumulated depreciation	185,237		187,565
Goodwill	183,673		183,673
Company-owned life insurance	77,158		76,729
Other real estate owned (“OREO”)	32,470		32,571
Accrued interest receivable	29,375		28,869
Mortgage servicing rights, net of accumulated amortization and impairment reserve	13,006		12,653
Deferred tax asset, net	2,965		2,597
Core deposit intangibles, net of accumulated amortization	5,582		5,937
Other assets	63,058		62,953
Total assets	$	7,439,317	$	7,721,761
Liabilities and Stockholders’ Equity
Deposits:
Non-interest bearing	$	1,406,892	$	1,495,309
Interest bearing	4,621,453		4,745,102
Total deposits	6,028,345		6,240,411
Securities sold under repurchase agreements	467,205		505,785
Accounts payable and accrued expenses	46,326		48,208
Accrued interest payable	6,433		6,502
Long-term debt	37,150		37,160
Other borrowed funds	8		32
Preferred stock pending redemption	—		50,000
Subordinated debentures held by subsidiary trusts	82,477		82,477
Total liabilities	6,667,944		6,970,575
Stockholders’ equity:
Nonvoting noncumulative preferred stock without par value; authorized 100,000 shares; no shares issued and outstanding as of March 31, 2013 and 5,000 shares issued and outstanding as of December 31, 2012	—		—
Common stock	274,929		271,335
Retained earnings	483,904		463,860
Accumulated other comprehensive income, net	12,540		15,991
Total stockholders’ equity	771,373		751,186
Total liabilities and stockholders’ equity	$	7,439,317	$	7,721,761

See accompanying notes to unaudited consolidated financial statements.

3

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES CONSOLIDATED STATEMENTS OF INCOME (In thousands, except per share data) (Unaudited)
	Three Months Ended March 31,
	2013			2012
Interest income:
Interest and fees on loans	$	55,493		$	57,910
Interest and dividends on investment securities:
Taxable	8,046			9,705
Exempt from federal taxes	1,226			1,204
Interest on deposits in banks	298			237
Interest on federal funds sold	4			1
Total interest income	65,067			69,057
Interest expense:
Interest on deposits	4,355			6,262
Interest on securities sold under repurchase agreements	100			156
Interest on long-term debt	480			498
Interest on preferred stock pending redemption	159			—
Interest on subordinated debentures held by subsidiary trusts	696			1,507
Total interest expense	5,790			8,423
Net interest income	59,277			60,634
Provision for loan losses	500			11,250
Net interest income after provision for loan losses	58,777			49,384
Non-interest income:
Income from the origination and sale of loans	10,675			8,384
Other service charges, commissions and fees	8,256			8,424
Wealth management revenues	4,134			3,283
Service charges on deposit accounts	4,068			4,161
Investment securities gains, net	8			31
Other income	1,678			2,099
Total non-interest income	28,819			26,382
Non-interest expense:
Salaries and wages	23,405			21,564
Employee benefits	8,175			8,966
Occupancy, net	4,026			3,988
Furniture and equipment	3,052			3,138
Outsourced technology services	2,157			2,266
OREO expense, net of income	1,896			1,105
FDIC insurance premiums	1,377			1,595
Professional fees	1,127			933
Mortgage servicing rights amortization	839			895
Mortgage servicing rights impairment recovery	(48		)	(868		)
Core deposit intangibles amortization	354			355
Other expenses	10,325			13,503
Total non-interest expense	56,685			57,440
Income before income tax expense	30,911			18,326
Income tax expense	10,867			6,112
Net income	20,044			12,214
Preferred stock dividends	—			853
Net income available to common shareholders	$	20,044		$	11,361
Basic earnings per common share	$	0.46		$	0.26
Diluted earnings per common share	$	0.46		$	0.26

See accompanying notes to unaudited consolidated financial statements.

4

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (In thousands) (Unaudited)
	Three Months Ended March 31,
	2013			2012
Net income	$	20,044		$	12,214
Other comprehensive income (loss), before tax:
Investment securities available-for sale:
Change in net unrealized gains (losses) during period	(5,717		)	755
Reclassification adjustment for net gains included in income	(8		)	(31		)
Defined benefit post-retirement benefits plans:
Change in net actuarial loss	35			33
Other comprehensive income (loss), before tax	(5,690		)	757
Deferred tax benefit (expense) related to other comprehensive income	2,239			(297		)
Other comprehensive income (loss), net of tax	(3,451		)	460
Comprehensive income, net of tax	$	16,593		$	12,674

See accompanying notes to unaudited consolidated financial statements.

5

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (In thousands, except share and per share data) (Unaudited)
	Preferred stock		Common stock			Retained earnings			Accumulated other comprehensive income			Total stockholders’ equity
Balance at December 31, 2012	$	—	$	271,335		$	463,860		$	15,991		$	751,186
Comprehensive income:
Net income	—		—			20,044			—			20,044
Other comprehensive income, net of tax	—		—			—			(3,451		)	(3,451		)
Common stock transactions:
25,677 common shares purchased and retired	—		(448		)	—			—			(448		)
108,873 non-vested common shares issued	—		—			—			—			—
1,815 non-vested common shares forfeited	—		—			—			—			—
243,238 stock options exercised, net of 87,933 shares tendered in payment of option price and income tax withholding amounts	—		3,145			—			—			3,145
Tax benefit of stock-based compensation	—		202			—			—			202
Stock-based compensation expense	—		695			—			—			695
Balance at March 31, 2013	$	—	$	274,929		$	483,904		$	12,540		$	771,373
Balance at December 31, 2011	$	50,000	$	266,842		$	435,144		$	19,034		$	771,020
Comprehensive income:
Net income	—		—			12,214			—			12,214
Other comprehensive income, net of tax	—		—			—			460			460
Common stock transactions:
17,904 common shares purchased and retired	—		(256		)	—			—			(256		)
2,358 common shares issued	—		—			—			—			—
122,912 non-vested common shares issued	—		—			—			—			—
1,556 non-vested common shares forfeited	—		—			—			—			—
100,991 stock options exercised, net of 37,397 shares tendered in payment of option price and income tax withholding amounts	—		1,068			—			—			1,068
Tax benefit of stock-based compensation	—		114			—			—			114
Stock-based compensation expense	—		643			—			—			643
Cash dividends declared:
Common ($0.12 per share)	—		—			(5,135		)	—			(5,135		)
Preferred (6.75% per share)	—		—			(853		)	—			(853		)
Balance at March 31, 2012	$	50,000	$	268,411		$	441,370		$	19,494		$	779,275

See accompanying notes to unaudited consolidated financial statements.

6

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES CONSOLIDATED STATEMENTS OF CASH FLOWS (In thousands) (Unaudited)
	Three Months Ended March 31,
	2013			2012
Cash flows from operating activities:
Net income	$	20,044		$	12,214
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	500			11,250
Net (gain) loss on disposal of property and equipment	(20		)	42
Depreciation and amortization	4,203			4,302
Net premium amortization on investment securities	4,082			2,678
Net gains on investment securities transactions	(8		)	(31		)
Net gains on sales of mortgage loans held for sale	(7,898		)	(5,927		)
Net gain on sale of OREO	(820		)	74
OREO valuation adjustments	2,305			578
Net reversal of impairment of mortgage servicing rights	(48		)	(868		)
Net gain on sale of mortgage servicing rights	—			(19		)
Deferred income tax expense (benefit)	1,853			(282		)
Net increase in cash surrender value of company-owned life insurance policies	(429		)	(462		)
Stock-based compensation expense	695			643
Tax benefits from stock-based compensation expense	202			114
Excess tax benefits from stock-based compensation	(165		)	(94		)
Originations of mortgage loans held for sale, net of sales	17,753			(272		)
Changes in operating assets and liabilities:
Decrease (increase) in interest receivable	(506		)	1,567
Decrease (increase) in other assets	(64		)	907
Increase (decrease) in accrued interest payable	(69		)	132
Increase (decrease) in accounts payable and accrued expenses	(1,861		)	1,744
Net cash provided by operating activities	39,749			28,290
Cash flows from investing activities:
Purchases of investment securities:
Held-to-maturity	(6,347		)	(7,592		)
Available-for-sale	(227,040		)	(222,413		)
Proceeds from maturities and pay-downs of investment securities:
Held-to-maturity	3,512			2,193
Available-for-sale	201,621			282,083
Proceeds from sales of mortgage servicing rights	311			907
Extensions of credit to customers, net of repayments	(22,997		)	10,027
Recoveries of loans charged-off	2,913			1,158
Proceeds from sales of OREO	3,957			5,691
Capital expenditures, net of sales	(650		)	(3,453		)
Net cash provided by (used in) investing activities	$	(44,720	)	$	68,601

7

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES CONSOLIDATED STATEMENTS OF CASH FLOWS (CONTINUED) (In thousands) (Unaudited)
	Three Months Ended March 31,
	2013			2012
Cash flows from financing activities:
Net increase (decrease) in deposits	$	(212,066	)	$	83,863
Net decrease in repurchase agreements	(38,580		)	(25,185		)
Net decrease in short-term borrowings	(24		)	(1		)
Repayments of long-term debt	(10		)	(9		)
Redemption of preferred stock	(50,000		)	—
Proceeds from issuance of common stock	3,145			1,068
Excess tax benefits from stock-based compensation	165			94
Purchase and retirement of common stock	(448		)	(256		)
Dividends paid to common stockholders	—			(5,135		)
Dividends paid to preferred stockholders	—			(853		)
Net cash provided by (used in) financing activities	(297,818		)	53,586
Net increase (decrease) in cash and cash equivalents	(302,789		)	150,477
Cash and cash equivalents at beginning of period	801,332			472,447
Cash and cash equivalents at end of period	$	498,543		$	622,924
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	$	3,376		$	100
Cash paid during the period for interest expense	$	5,859		$	8,291

See accompanying notes to unaudited consolidated financial statements.

8

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

(1) Basis of Presentation

In the opinion of management, the accompanying unaudited consolidated financial statements of First Interstate BancSystem, Inc. and subsidiaries (the “Company”) contain all adjustments (all of which are of a normal recurring nature) necessary to present fairly the financial position of the Company at March 31, 2013 and December 31, 2012, and the results of operations and cash flows for each of the three month periods ended March 31, 2013 and 2012, in conformity with U.S. generally accepted accounting principles. The balance sheet information at December 31, 2012 is derived from audited consolidated financial statements. Certain reclassifications, none of which were material, have been made to conform prior year financial statements to the March 31, 2013 presentation. These reclassifications did not change previously reported net income or stockholders’ equity.

These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2012. Operating results for the three months ended March 31, 2013 are not necessarily indicative of the results that may be expected for the year ending December 31, 2013.

(2) Investment Securities

The amortized cost and approximate fair values of investment securities are summarized as follows:

March 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-Sale:
Obligations of U.S. government agencies	$	777,044	$	3,220	$	(342	)	$	779,922
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,210,425		23,814		(3,501		)	1,230,738
Private mortgage-backed securities	495		15		(1		)	509
Total	$	1,987,964	$	27,049	$	(3,844	)	$	2,011,169

March 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Held-to Maturity:
State, county and municipal securities	$	192,241	$	9,881	$	(282	)	$	201,840
Corporate securities	18,185		96		(6		)	18,275
Total	$	210,426	$	9,977	$	(288	)	$	220,115

December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-Sale:
Obligations of U.S. government agencies	$	751,501	$	3,518	$	(163	)	$	754,856
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,214,377		27,000		(1,526		)	1,239,851
Private mortgage-backed securities	539		13		(1		)	551
Total	$	1,966,417	$	30,531	$	(1,690	)	$	1,995,258

9

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Held-to Maturity:
State, county and municipal securities	$	192,875	$	10,835	$	(176	)	$	203,534
Corporate securities	14,975		64		(13		)	15,026
Other securities	373		—		—			373
Total	$	208,223	$	10,899	$	(189	)	$	218,933

Gross realized gains and losses from the disposition of investment securities are summarized in the following table:

	Three Months Ended March 31,
	2013		2012
Gross realized gains	$	8	$	31
Gross realized losses	—		—

The following tables show the gross unrealized losses and fair values of investment securities, aggregated by investment category, and the length of time individual investment securities have been in a continuous unrealized loss position, as of March 31, 2013 and December 31, 2012

	Less than 12 Months					12 Months or More					Total
March 31, 2013	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale:
Obligations of U.S. government agencies	$	182,957	$	(342	)	$	—	$	—		$	182,957	$	(342	)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	365,181		(3,501		)	—		—			365,181		(3,501		)
Private mortgage-backed securities	—		—			125		(1		)	125		(1		)
Total	$	548,138	$	(3,843	)	$	125	$	(1	)	$	548,263	$	(3,844	)

	Less than 12 Months					12 Months or More					Total
March 31, 2013	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Held-to-Maturity:
State, county and municipal securities	$	24,188	$	(276	)	$	525	$	(6	)	$	24,713	$	(282	)
Corporate securities	3,239		(6		)	—		—			3,239		(6		)
Total	$	27,427	$	(282	)	$	525	$	(6	)	$	27,952	$	(288	)

	Less than 12 Months					12 Months or More					Total
December 31, 2012	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale:
Obligations of U.S. government agencies	$	93,982	$	(163	)	$	—	$	—		$	93,982	$	(163	)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	250,198		(1,526		)	—		—			250,198		(1,526		)
Private mortgage-backed securities	—		—			137		(1		)	137		(1		)
Total	$	344,180	$	(1,689	)	$	137	$	(1	)	$	344,317	$	(1,690	)

10

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

	Less than 12 Months					12 Months or More					Total
December 31, 2012	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Held-to-Maturity:
State, county and municipal securities	$	19,389	$	(168	)	$	557	$	(8	)	$	19,946	$	(176	)
Corporate securities	9,312		(13		)	—		—			9,312		(13		)
Total	$	28,701	$	(181	)	$	557	$	(8	)	$	29,258	$	(189	)

The investment portfolio is evaluated quarterly for other-than-temporary declines in the market value of each individual investment security. The Company had 91 and 69 individual investment securities that were in an unrealized loss position as of March 31, 2013 and December 31, 2012, respectively. Unrealized losses as of March 31, 2013 and December 31, 2012 related primarily to fluctuations in the current interest rates. The Company does not have the intent to sell any of the available-for-sale securities in the above table and it is not likely that the Company will have to sell any such securities before a recovery in cost. No impairment losses were recorded during the three months ended March 31, 2013 and 2012.

Maturities of investment securities at March 31, 2013 are shown below. Maturities of mortgage-backed securities have been adjusted to reflect shorter maturities based upon estimated prepayments of principal. All other investment securities maturities are shown at contractual maturity dates.

	Available-for-Sale				Held-to-Maturity
March 31, 2013	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Within one year	$	400,147	$	405,641	$	3,877	$	3,925
After one year but within five years	1,127,952		1,141,233		52,321		53,266
After five years but within ten years	375,101		378,108		86,803		90,886
After ten years	84,764		86,187		67,425		72,038
Total	$	1,987,964	$	2,011,169	$	210,426	$	220,115

As of March 31, 2013, the Company had investment securities callable within one year with amortized costs and estimated fair values of $438,562 and $438,990, respectively, including callable structured notes with amortized costs and estimated fair values of $130,375 and $130,572, respectively. These investment securities are primarily classified as available-for-sale and included in the after one year but within five years category in the table above.

11

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

(3) Loans

The following table presents loans by class as of the dates indicated:

	March 31, 2013		December 31, 2012
Real estate loans:
Commercial	$	1,469,302	$	1,497,272
Construction:
Land acquisition & development	215,505		220,196
Residential	50,153		49,274
Commercial	65,228		65,059
Total construction loans	330,886		334,529
Residential	758,480		708,339
Agricultural	172,522		177,244
Total real estate loans	2,731,190		2,717,384
Consumer:
Indirect consumer	444,257		438,245
Other consumer	135,474		137,743
Credit card	56,633		60,806
Total consumer loans	636,364		636,794
Commercial	688,844		688,753
Agricultural	111,411		113,627
Other, including overdrafts	1,307		912
Loans held for investment	4,169,116		4,157,470
Mortgage loans held for sale	55,443		66,442
Total loans	$	4,224,559	$	4,223,912

12

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The following tables present the contractual aging of the Company’s recorded investment in past due loans by class as of the period indicated:

							Total Loans
	30 - 59		60 - 89		> 90		30 or More
	Days		Days		Days		Days		Current		Non-accrual		Total
As of March 31, 2013	Past Due		Past Due		Past Due		Past Due		Loans		Loans		Loans
Real estate
Commercial	$	12,846	$	865	$	—	$	13,711	$	1,410,640	$	44,951	$	1,469,302
Construction:
Land acquisition & development	6,294		62		—		6,356		192,376		16,773		215,505
Residential	92		—		—		92		48,726		1,335		50,153
Commercial	2,173		—		—		2,173		56,572		6,483		65,228
Total construction loans	8,559		62		—		8,621		297,674		24,591		330,886
Residential	4,269		502		1,044		5,815		744,108		8,557		758,480
Agricultural	1,464		349		2		1,815		166,116		4,591		172,522
Total real estate loans	27,138		1,778		1,046		29,962		2,618,538		82,690		2,731,190
Consumer:
Indirect consumer	2,166		326		3		2,495		441,477		285		444,257
Other consumer	642		157		1		800		133,786		888		135,474
Credit card	308		222		467		997		55,614		22		56,633
Total consumer loans	3,116		705		471		4,292		630,877		1,195		636,364
Commercial	4,097		3,966		329		8,392		665,884		14,568		688,844
Agricultural	813		311		95		1,219		110,051		141		111,411
Other, including overdrafts			—		—		—		1,307		—		1,307
Loans held for investment	35,164		6,760		1,941		43,865		4,026,657		98,594		4,169,116
Mortgage loans originated for sale	—		—		—		—		55,443		—		55,443
Total loans	$	35,164	$	6,760	$	1,941	$	43,865	$	4,082,100	$	98,594	$	4,224,559

13

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

							Total Loans
	30 - 59		60 - 89		> 90		30 or More
	Days		Days		Days		Days		Current		Non-accrual		Total
As of December 31, 2012	Past Due		Past Due		Past Due		Past Due		Loans		Loans		Loans
Real estate
Commercial	$	5,449	$	3,163	$	2	$	8,614	$	1,438,142	$	50,516	$	1,497,272
Construction:
Land acquisition & development	3,371		2,121		318		5,810		195,077		19,309		220,196
Residential	283		—		—		283		46,816		2,175		49,274
Commercial	—		—		—		—		56,933		8,126		65,059
Total construction loans	3,654		2,121		318		6,093		298,826		29,610		334,529
Residential	3,896		969		1,085		5,950		691,963		10,426		708,339
Agricultural	1,187		—		218		1,405		171,009		4,830		177,244
Total real estate loans	14,186		6,253		1,623		22,062		2,599,940		95,382		2,717,384
Consumer:
Indirect consumer	3,218		512		32		3,762		434,200		283		438,245
Other consumer	1,044		104		31		1,179		135,574		990		137,743
Credit card	409		278		392		1,079		59,704		23		60,806
Total consumer loans	4,671		894		455		6,020		629,478		1,296		636,794
Commercial	5,463		1,064		216		6,743		671,414		10,596		688,753
Agricultural	1,710		361		—		2,071		111,031		525		113,627
Other, including overdrafts	—		—		—		—		912		—		912
Loans held for investment	26,030		8,572		2,294		36,896		4,012,775		107,799		4,157,470
Mortgage loans originated for sale	—		—		—		—		66,442		—		66,442
Total loans	$	26,030	$	8,572	$	2,294	$	36,896	$	4,079,217	$	107,799	$	4,223,912

If interest on non-accrual loans had been accrued, such income would have approximated $1,352 and $2,702 for the three months ended March 31, 2013 and 2012, respectively.

14

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The Company considers impaired loans to include all loans risk rated doubtful, loans placed on non-accrual status and loans renegotiated in troubled debt restructurings with the exception of consumer loans. The following tables present information on the Company’s recorded investment in impaired loans as of dates indicated:

As of March 31, 2013	Unpaid Total Principal Balance		Recorded Investment With No Allowance		Recorded Investment With Allowance		Total Recorded Investment		Related Allowance
Real estate:
Commercial	$	82,456	$	34,042	$	38,695	$	72,737	$	4,429
Construction:
Land acquisition & development	25,929		13,976		6,560		20,536		1,703
Residential	1,925		1,335		—		1,335		—
Commercial	9,422		6,227		256		6,483		68
Total construction loans	37,276		21,538		6,816		28,354		1,771
Residential	11,649		6,181		2,595		8,776		1,132
Agricultural	5,415		1,724		3,098		4,822		1,035
Total real estate loans	136,796		63,485		51,204		114,689		8,367
Commercial	16,521		7,969		7,863		15,832		3,725
Agricultural	205		127		25		152		25
Total	$	153,522	$	71,581	$	59,092	$	130,673	$	12,117

As of December 31, 2012	Unpaid Total Principal Balance		Recorded Investment With No Allowance		Recorded Investment With Allowance		Total Recorded Investment		Related Allowance
Real estate:
Commercial	$	84,300	$	39,049	$	34,774	$	73,823	$	4,112
Construction:
Land acquisition & development	28,558		15,891		7,173		23,064		1,457
Residential	3,018		1,976		710		2,686		251
Commercial	10,447		7,785		340		8,125		69
Total construction loans	42,023		25,652		8,223		33,875		1,777
Residential	13,271		6,152		4,495		10,647		1,677
Agricultural	5,559		1,834		3,227		5,061		784
Total real estate loans	145,153		72,687		50,719		123,406		8,350
Commercial	12,770		9,036		3,206		12,242		1,919
Agricultural	589		509		28		537		28
Total	$	158,512	$	82,232	$	53,953	$	136,185	$	10,297

15

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The following table presents the average recorded investment in and income recognized on impaired loans for the periods indicated:

	Three Months Ended March 31,
	2013				2012
	Average Recorded Investment		Income Recognized		Average Recorded Investment		Income Recognized
Real estate:
Commercial	$	73,936	$	338	$	88,657	$	188
Construction:
Land acquisition & development	22,641		441		62,227		3
Residential	2,259		—		9,208		18
Commercial	7,898		—		24,265		—
Total construction loans	32,798		441		95,700		21
Residential	10,519		4		18,072		160
Agricultural	4,948		4		7,268		56
Total real estate loans	122,201		787		209,697		425
Commercial	12,746		18		17,885		31
Agricultural	632		4		1,234		—
Total	$	135,579	$	809	$	228,816	$	456

The amount of interest income recognized by the Company within the period that the loans were impaired was primarily related to loans modified in a troubled debt restructuring that remained on accrual status. Interest payments received on non-accrual impaired loans are applied to principal. Interest income is subsequently recognized only to the extent cash payments are received in excess of principal due. If interest on impaired loans had been accrued, interest income on impaired loans would have been approximately $1,335 and $2,683 for the three months ended March 31, 2013 and 2012, respectively.

Collateralized impaired loans are generally recorded at the fair value of the underlying collateral using discounted cash flows, independent appraisals and management estimates based upon current market conditions. For loans measured under the present value of cash flows method, the change in present value attributable to the passage of time, if applicable, is recognized in the provision for loan losses and thus no interest income is recognized.

Modifications of performing loans are made in the ordinary course of business and are completed on a case-by-case basis as negotiated with the borrower. Loan modifications typically include interest rate concessions, interest only periods of less than twelve months, short-term payment deferrals and extension of amortization periods to provide payment relief. A loan modification is considered a troubled debt restructuring if the borrower is experiencing financial difficulties and the Company, for economic or legal reasons, grants a concession to the borrower that it would not otherwise consider. Certain troubled debt restructurings are on non-accrual status at the time of restructuring and are typically returned to accrual status after considering the borrower's sustained repayment performance in accordance with the restructuring agreement for a period of at least six months and management is reasonably assured of future performance. If the troubled debt restructuring meets these performance criteria and the interest rate granted at the modification is equal to or greater than the rate that the Company was willing to accept at the time of the restructuring for a new loan with comparable risk, then the loan will return to performing status and the accrual of interest will resume.

The Company had loans renegotiated in troubled debt restructurings of $75,229 as of March 31, 2013, of which $39,442 were included in non-accrual loans and $35,787 were on accrual status. The Company had loans renegotiated in troubled debt restructurings of $76,597 as of December 31, 2012, of which $44,665 were included in non-accrual loans and $31,932 were on accrual status.

16

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The following table presents information on the Company's troubled debt restructurings that occurred during the three months ended March 31, 2013:    

	Number of Notes	Type of Concession								Principal Balance at Restructure Date
Three Months Ended March 31, 2013		Interest only period		Extension of terms or maturity		Interest rate adjustment		Other (1)
Real estate:
Commercial	11	$	120	$	389	$	5,345	$	183	$	6,037
Total real estate loans	11	120		389		5,345		183		6,037
Commercial	4	50		178		265		87		580
Total loans restructured during period	15	$	170	$	567	$	5,610	$	270	$	6,617

(1) Other includes concessions that reduce or defer payments for a specified period of time and/or do not fit into other designated categories.

For troubled debt restructurings that were on non-accrual status or otherwise deemed impaired before the modification, a specific reserve may already be recorded. In periods subsequent to modification, the Company continues to evaluate all troubled debt restructurings for possible impairment and recognizes impairment through the allowance. Additionally these loans continue to work their way through the credit cycle through charge-off, pay-off or foreclosure. Financial effects of modifications of troubled debt restructurings may include principal loan forgiveness or other charge-offs directly related to the restructuring. The Company had no charge-offs directly related to modifying troubled debt restructurings during the three months ended March 31, 2013 or 2012.

The following table presents information on the Company's troubled debt restructurings during the previous 12 months for which there was a payment default during the periods indicated. The Company considers a payment default to occur on troubled debt restructurings when the loan is 90 days or more past due or was placed on non-accrual status after the modification.

	Three Months Ended March 31,
	Number of Notes	Balance
Residential real estate	1	$	278
Commercial	1	372
Total	2	$	650

At March 31, 2013, there were no material commitments to lend additional funds to borrowers whose existing loans have been renegotiated or are classified as non-accrual.

As part of the on-going and continuous monitoring of the credit quality of the Company’s loan portfolio, management tracks internally assigned risk classifications of loans. The Company adheres to a Uniform Classification System developed jointly by the various bank regulatory agencies to internally risk rate loans. The Uniform Classification System defines three broad categories of criticized assets, which the Company uses as credit quality indicators:

Other Assets Especially Mentioned — includes loans that exhibit weaknesses in financial condition, loan structure or documentation, which if not promptly corrected, may lead to the development of abnormal risk elements.

Substandard — includes loans that are inadequately protected by the current sound worth and paying capacity of the borrower. Although the primary source of repayment for a Substandard is not currently sufficient; collateral or other sources of repayment are sufficient to satisfy the debt. Continuance of a Substandard loan is not warranted unless positive steps are taken to improve the worthiness of the credit.

Doubtful — includes loans that exhibit pronounced weaknesses to a point where collection or liquidation in full, on the basis of currently existing facts, conditions and values, is highly questionable and improbable. Doubtful loans are required to be placed on non-accrual status and are assigned specific loss exposure.

17

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The following tables present the Company’s recorded investment in criticized loans by class and credit quality indicator based on the most recent analysis performed as of the dates indicated:

As of March 31, 2013	Other Assets Especially Mentioned		Substandard		Doubtful		Total Criticized Loans
Real estate:
Commercial	$	89,207	$	127,083	$	16,110	$	232,400
Construction:
Land acquisition & development	29,171		22,977		4,231		56,379
Residential	2,132		1,728		801		4,661
Commercial	3,000		695		5,788		9,483
Total construction loans	34,303		25,400		10,820		70,523
Residential	9,890		11,185		2,981		24,056
Agricultural	19,062		6,705		3,097		28,864
Total real estate loans	152,462		170,373		33,008		355,843
Consumer:
Indirect consumer	704		1,660		79		2,443
Other consumer	587		1,120		436		2,143
Credit card	—		447		2,281		2,728
Total consumer loans	1,291		3,227		2,796		7,314
Commercial	41,399		22,072		7,996		71,467
Agricultural	2,493		1,423		25		3,941
Total	$	197,645	$	197,095	$	43,825	$	438,565

As of December 31, 2012	Other Assets Especially Mentioned		Substandard		Doubtful		Total Criticized Loans
Real estate:
Commercial	$	101,936	$	135,282	$	15,173	$	252,391
Construction:
Land acquisition & development	28,137		25,884		4,739		58,760
Residential	2,531		2,427		1,143		6,101
Commercial	3,000		795		7,383		11,178
Total construction loans	33,668		29,106		13,265		76,039
Residential	9,542		11,680		4,511		25,733
Agricultural	18,490		6,737		3,228		28,455
Total real estate loans	163,636		182,805		36,177		382,618
Consumer:
Indirect consumer	793		1,764		114		2,671
Other consumer	684		1,395		628		2,707
Credit card	—		415		2,085		2,500
Total consumer loans	1,477		3,574		2,827		7,878
Commercial	42,223		27,184		3,428		72,835
Agricultural	2,596		1,625		28		4,249
Total	$	209,932	$	215,188	$	42,460	$	467,580

18

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The Company maintains a credit review function, which is independent of the credit approval process, to assess assigned internal risk classifications and monitor compliance with internal lending policies and procedures. Written action plans with firm target dates for resolution of identified problems are maintained and reviewed on a quarterly basis for all categories of criticized loans.

(4) Allowance For Loan Losses

The following tables present a summary of changes in the allowance for loan losses by portfolio segment for the periods indicated.

Three Months Ended March 31, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
Allowance for loan losses:
Beginning balance	$	75,782		$	7,140		$	17,073		$	504		$	12	$	100,511
Provision charged to operating expense	(1,035		)	537			1,015			(23		)	6		500
Less loans charged-off	(4,143		)	(1,062		)	(811		)	(4		)	—		(6,020		)
Add back recoveries of loans previously    charged-off	1,062			473			1,375			3			—		2,913
Ending balance	$	71,666		$	7,088		$	18,652		$	480		$	18	$	97,904
Loans individually evaluated for impairment	$	8,367		$	—		$	3,725		$	25		$	—	$	12,117
Loans collectively evaluated for impairment	63,299			7,088			14,927			455			18		85,787
Allowance for loan losses	$	71,666		$	7,088		$	18,652		$	480		$	18	$	97,904
Total loans:
Individually evaluated for impairment	$	114,690		$	—		$	15,832		$	152		$	—	$	130,674
Collectively evaluated for impairment	2,671,943			636,364			673,012			111,259			1,307		4,093,885
Total loans	$	2,786,633		$	636,364		$	688,844		$	111,411		$	1,307	$	4,224,559

Three Months Ended March 31, 2012	Real Estate			Consumer			Commercial			Agriculture			Other		Total
Allowance for loan losses:
Beginning balance	$	87,396		$	8,594		$	15,325		$	1,266		$	—	$	112,581
Provision charged to operating expense	6,382			(591		)	5,441			18			—		11,250
Less loans charged-off	(5,156		)	(1,312		)	(2,512		)	(107		)	—		(9,087		)
Add back recoveries of loans previously    charged-off	506			521			126			5			—		1,158
Ending balance	$	89,128		$	7,212		$	18,380		$	1,182		$	—	$	115,902

Loans individually evaluated for impairment	$	26,673	$	—	$	4,126	$	491	$	—	$	31,290
Loans collectively evaluated for impairment	62,455		7,212		14,254		691		—		84,612
Allowance for loan losses	$	89,128	$	7,212	$	18,380	$	1,182	$	—	$	115,902
Total loans:
Individually evaluated for impairment	$	198,033	$	—	$	13,559	$	1,514	$	—	$	213,106
Collectively evaluated for impairment	2,516,946		606,073		694,838		127,085		568		3,945,510
Total loans	$	2,714,979	$	606,073	$	708,397	$	128,599	$	568	$	4,158,616

19

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The Company performs a quarterly assessment of the adequacy of its allowance for loan losses in accordance with generally accepted accounting principles. The methodology used to assess the adequacy is consistently applied to the Company's loan portfolio and consists of three elements: (1) specific valuation allowances based on probable losses on impaired loans; (2) historical valuation allowances based on loan loss experience for similar loans with similar characteristics and trends; and (3) general valuation allowances determined based on changes in the nature of the loan portfolio, overall portfolio quality, industry concentrations, delinquency trends, general economic conditions and other qualitative risk factors both internal and external to the Company.

Specific allowances are established for loans where management has determined that probability of a loss exists by analyzing the borrower’s ability to repay amounts owed, collateral deficiencies and any relevant qualitative or economic factors impacting the loan. Historical valuation allowances are determined by applying percentage loss factors to the credit exposures from outstanding loans. For commercial, agricultural and real estate loans, loss factors are applied based on the internal risk classifications of these loans. For consumer loans, loss factors are applied on a portfolio basis. For commercial, agriculture and real estate loans, loss factor percentages are based on a migration analysis of our historical loss experience, designed to account for credit deterioration. For consumer loans, loss factor percentages are based on a one-year loss history. General valuation allowances are determined by evaluating, on a quarterly basis, changes in the nature and volume of the loan portfolio, overall portfolio quality, industry concentrations, current economic and regulatory conditions and the estimated impact of these factors on historical loss rates.

(5) Other Real Estate Owned

Information with respect to the Company's other real estate owned follows:

	Three Months Ended March 31,
	2013			2012
Beginning balance	$	32,571		$	37,452
Additions	5,331			13,978
Capitalized improvements	10			(331		)
Valuation adjustments	(2,305		)	(578		)
Dispositions	(3,137		)	(5,765		)
Ending balance	$	32,470		$	44,756

(6) Capital Stock

The Company had 18,424,252 and 17,635,369 shares of Class A common stock outstanding as of March 31, 2013 and December 31, 2012, respectively.

The Company had 25,190,690 and 25,654,954 shares of Class B common stock outstanding as of March 31, 2013 and December 31, 2012, respectively.

On December 31, 2012, the Company provides notice to holders of the Series A noncummulative redeemable preferred stock ("Series A Preferred Stock") of its intention to redeem the Series A Preferred Stock on January 18, 2013. Upon notice to holders of the redemption, the Series A Preferred Stock was reclassified from stockholders' equity to a liability. The aggregate redemption price for the Series A Preferred Stock was $50,150.

(7) Earnings per Common Share

Basic earnings per common share is calculated by dividing net income by the weighted average number of common shares outstanding during the period presented, excluding unvested restricted stock. Diluted earnings per share is calculated by dividing net income by the weighted average number of common shares determined for the basic earnings per share computation plus the dilutive effects of stock-based compensation using the treasury stock method.

20

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The following table sets forth the computation of basic and diluted earnings per share for the three month periods ended March 31, 2013 and 2012.

	Three Months Ended March 31,
	2013		2012
Net income	$	20,044	$	12,214
Less preferred stock dividends	—		853
Net income available to common shareholders, basic and diluted	$	20,044	$	11,361
Weighted average common shares outstanding for basic earnings per share computation	43,140,409		42,873,769
Dilutive effects of stock-based compensation	287,973		108,774
Weighted average common shares outstanding for diluted earnings per common share computation	43,428,382		42,982,543
Basic earnings per common share	$	0.46	$	0.26
Diluted earnings per common share	$	0.46	$	0.26

The Company had 1,025,419 and 2,657,668 stock options outstanding as of March 31, 2013 and 2012, respectively, that were not included in the computation of diluted earnings per common share because their effect would be anti-dilutive. The Company had 61,760 and 48,196 shares of unvested restricted stock as of March 31, 2013 and 2012, respectively, that were not included in the computation of diluted earnings per common share because performance conditions for vesting had not been met.

(8) Regulatory Capital

The Company is subject to the regulatory capital requirements administered by federal banking regulators and the Federal Reserve. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company must meet specific capital guidelines that involve quantitative measures of the Company’s assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. Quantitative measures established by regulation to ensure capital adequacy require the Company to maintain minimum amounts and ratios of total and tier 1 capital to risk-weighted assets, and of tier 1 capital to average assets, as defined in the regulations. As of March 31, 2013 and December 31, 2012, the Company exceeded all capital adequacy requirements to which it is subject.

Actual capital amounts and ratios and selected minimum regulatory thresholds for the Company and its bank subsidiary, First Interstate Bank (“FIB”), as of March 31, 2013 and December 31, 2012 are presented in the following tables:

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
March 31, 2013
Total risk-based capital:
Consolidated	$	766,478	15.9	%	$	385,443	8.0	%	NA		NA
FIB	707,053		14.7		383,593		8.0		$	479,491	10.0	%
Tier 1 risk-based capital:
Consolidated	677,787		14.1		192,721		4.0		NA		NA
FIB	634,648		13.2		191,796		4.0		$	287,695	6.0
Leverage capital ratio:
Consolidated	677,787		9.2		293,323		4.0		NA		NA
FIB	634,648		8.7		292,739		4.0		$	365,924	5.0

21

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
December 31, 2012
Total risk-based capital:
Consolidated	$	748,431	15.6	%	$	384,014	8.0	%	NA		NA
FIB	697,695		14.6		382,245		8.0		$	477,806	10.0	%
Tier 1 risk-based capital:
Consolidated	652,929		13.6		192,007		4.0		NA		NA
FIB	622,466		13.0		191,122		4.0		$	286,683	6.0
Leverage capital ratio:
Consolidated	652,929		8.8		296,559		4.0		NA		NA
FIB	622,466		8.4		296,061		4.0		$	370,077	5.0

(9) Commitments and Contingencies

In the normal course of business, the Company is involved in various claims and litigation. In the opinion of management, following consultation with legal counsel, the ultimate liability or disposition thereof is not expected to have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company.

The Company had commitments under construction contracts of $67 as of March 31, 2013.

The Company had commitments to purchase held-to-maturity municipal securities of $960 as of March 31, 2013.

(10) Financial Instruments with Off-Balance Sheet Risk

The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the commitment contract. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. At March 31, 2013, commitments to extend credit to existing and new borrowers approximated $1,176,789 which included $362,247 on unused credit card lines and $304,030 with commitment maturities beyond one year.

Standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. At March 31, 2013, the Company had outstanding standby letters of credit of $71,407. The estimated fair value of the obligation undertaken by the Company in issuing the standby letters of credit is included in other liabilities in the Company’s consolidated balance sheet.

(11) Supplemental Disclosures to Consolidated Statement of Cash Flows

The Company transferred loans of $5,331 and $13,978 to OREO during the three months endedMarch 31, 2013 and 2012, respectively.

The Company transferred internally originated mortgage servicing rights of $1,144 and $1,040 from loans to mortgage servicing assets during the three months endedMarch 31, 2013 and 2012, respectively.

The Company reclassified tax credit investments with a carrying value of $429 from held-to-maturity investment securities to other assets during the three months endedMarch 31, 2013.

22

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

(12) Other Comprehensive Income

The gross amounts of each component of other comprehensive income and the related tax effects are as follows:

	Pre-tax						Tax Expense (Benefit)						Net of Tax
Three Months Ended March 31,	2013			2012			2013			2012			2013			2012
Investment securities available-for sale:
Change in net unrealized gain during period	$	(5,717	)	$	755		$	(2,250	)	$	296		$	(3,467	)	$	459
Reclassification adjustment for net gains included in net income	(8		)	(31		)	(3		)	(12		)	(5		)	(19		)
Defined benefits post-retirement benefit plan:
Change in net actuarial loss	35			33			14			13			21			20
Total other comprehensive income	$	(5,690	)	$	757		$	(2,239	)	$	297		$	(3,451	)	$	460

The components of accumulated other comprehensive income, net of income taxes, are as follows:

	March 31, 2013			December 31, 2012
Net unrealized gain on investment securities available-for-sale	$	14,065		$	17,537
Net actuarial loss on defined benefit post-retirement benefit plans	(1,525		)	(1,546		)
Net accumulated other comprehensive income	$	12,540		$	15,991

(13) Fair Value Measurements

Financial assets and financial liabilities measured at fair value on a recurring basis are as follows:

			Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale:
Obligations of U.S. government agencies	$	779,922	$	—	$	779,922	$	—
U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,230,738		—		1,230,738		—
Private mortgage-backed securities	509		—		509		—
Mortgage servicing rights	18,807		—		18,807		—

23

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

			Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale:
Obligations of U.S. government agencies	$	754,856	$	—	$	754,856	$	—
U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,239,851		—		1,239,851		—
Private mortgage-backed securities	551		—		551		—
Mortgage servicing rights	16,373		—		16,373		—

There were no transfers between levels of the fair value hierarchy during the three months endedMarch 31, 2013 or 2012.

The methodologies used by the Company in determining the fair values of each class of financial instruments are based primarily on the use of independent, market-based data to reflect a value that would be reasonably expected in an orderly transaction between market participants at the measurement date. The Company obtains fair value measurements for investment securities from an independent pricing service and evaluates mortgage servicing rights for impairment using an independent valuation service. The vendors chosen by the Company are widely recognized vendors whose evaluations support the pricing functions of financial institutions, investment and mutual funds, and portfolio managers. The Company has documented and evaluated the pricing methodologies used by the vendors and maintains internal processes that regularly test valuations. These internal processes include obtaining and reviewing available reports on internal controls, evaluating the prices for reasonableness given market changes, obtaining and evaluating the inputs used in the model for a sample of securities, investigating anomalies and confirming determinations through discussions with the vendor. For investment securities, if needed, a broker may be utilized to determine the reported fair value. Further details on the methods used to estimate the fair value of each class of financial instruments above are discussed below:

Investment Securities Available-for-Sale. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the investment's terms and conditions, among other things.

Mortgage Servicing Rights. Mortgage servicing rights are initially recorded at fair value based on comparable market quotes and are amortized in proportion to and over the period of estimated net servicing income. Mortgage servicing rights are evaluated quarterly for impairment using an independent valuation service. The valuation service utilizes discounted cash flow modeling techniques, which consider observable data that includes market consensus prepayment speeds and the predominant risk characteristics of the underlying loans including loan type, note rate and loan term. Management believes the significant inputs utilized in the valuation model are observable in the market.

Additionally, from time to time, certain assets are measured at fair value on a non-recurring basis. Adjustments to fair value generally result from the application of lower-of-cost-or-market accounting or write-downs of individual assets due to impairment.

24

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The following table presents information about the Company’s assets and liabilities measured at fair value on a non-recurring basis.

			Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Impaired loans	$	77,089	$	—	$	—	$	77,089
Other real estate owned	14,372		—		—		14,372
Long-lived assets to be disposed of by sale	496		—		—		496
			Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Impaired loans	$	74,623	$	—	$	—	$	74,623
Other real estate owned	15,745		—		—		15,745
Long-lived assets to be disposed of by sale	496		—		—		496

Impaired Loans. Collateralized impaired loans are reported at the fair value of the underlying collateral if repayment is expected solely from collateral. The impaired loans are reported at fair value through specific valuation allowance allocations. In addition, when it is determined that the fair value of an impaired loan is less than the recorded investment in the loan, the carrying value of the loan is adjusted to fair value through a charge to the allowance for loan losses. Collateral values are estimated using independent appraisals and management estimates of current market conditions. As of March 31, 2013, certain impaired loans with a carrying value of $112,054 were reduced by specific valuation allowance allocations of $12,117 and partial loan charge-offs of $22,848 resulting in a reported fair value of $77,089. As of December 31, 2012, certain impaired loans with a carrying value of $107,247 were reduced by specific valuation allowance allocations of $10,297 and partial loan charge-offs of $22,327 resulting in a reported fair value of $74,623.

OREO.The fair values of OREO are estimated using independent appraisals and management estimates of current market conditions. Upon initial recognition, write-downs based on the foreclosed asset's fair value at foreclosure are reported through charges to the allowance for loan losses. Periodically, the fair value of foreclosed assets is remeasured with any subsequent write-downs charged to OREO expense in the period in which they are identified. Write-downs of $2,305 during the three months ended March 31, 2013 were based on management estimates of the current fair value of properties. Write-downs of $578 during the three months ended March 31, 2012 included adjustments of $511 directly related to receipt of updated appraisals and $67 based on management estimates of the current fair value of properties.

Long-lived Assets to be Disposed of by Sale. Long-lived assets to be disposed of by sale are carried at the lower of carrying value or fair value less estimated costs to sell. The fair values of long-lived assets to be disposed of by sale are based upon observable market data and management estimates of current market conditions. As of March 31, 2013 and December 31, 2012, the Company had a long-lived asset to be disposed of by sale with a carrying value of $566 that had been reduced by write-downs of $70 resulting in a reported fair value of $496.

In addition, mortgage loans held for sale are required to be measured at the lower of cost or fair value. The fair value of mortgage loans held for sale is based upon binding contracts or quotes or bids from third party investors. As of March 31, 2013 and December 31, 2012, all mortgage loans held for sale were recorded at cost.

25

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The Company is required to disclose the fair value of financial instruments for which it is practical to estimate fair value. The methodologies for estimating the fair value of financial instruments that are measured at fair value on a recurring or non-recurring basis are discussed above. The methodologies for estimating the fair value of other financial instruments are discussed below. For financial instruments bearing a variable interest rate where no credit risk exists, it is presumed that recorded book values are reasonable estimates of fair value.

Financial Assets. Carrying values of cash, cash equivalents and accrued interest receivable approximate fair values due to the liquid and/or short-term nature of these instruments. Fair values for investment securities held-to-maturity are obtained from an independent pricing service, which considers observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the investment’s terms and conditions, among other things. Fair values of fixed rate loans and variable rate loans that reprice on an infrequent basis are estimated by discounting future cash flows using current interest rates at which similar loans with similar terms would be made to borrowers of similar credit quality. Carrying values of variable rate loans that reprice frequently, and with no change in credit risk, approximate the fair values of these instruments.

Financial Liabilities. The fair values of demand deposits, savings accounts, securities sold under repurchase agreements and accrued interest payable are the amounts payable on demand at the reporting date. The fair values of fixed-maturity certificates of deposit are estimated using external market rates currently offered for deposits with similar remaining maturities. The carrying values of the interest bearing demand notes to the United States Treasury are deemed an approximation of fair values due to the frequent repayment and repricing at market rates. The floating rate subordinated debenture, floating rate subordinated term loan, notes payable to the FHLB, fixed rate subordinated term debt, and capital lease obligation are estimated by discounting future cash flows using current rates for advances with similar characteristics. The carrying value of the preferred stock pending redemption approximated fair value due to the short-term nature of the instrument.

Commitments to Extend Credit and Standby Letters of Credit. The fair value of commitments to extend credit and standby letters of credit, based on fees currently charged to enter into similar agreements, is not significant.

26

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

The estimated fair values of financial instruments that are reported at amortized cost in the Company's consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, are as follows:

					Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Carrying Amount		Estimated Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	$	498,543	$	498,543	$	—	$	498,543	$	—
Investment securities available-for-sale	2,011,169		2,011,169		—		2,011,169		—
Investment securities held-to-maturity	210,426		220,115		—		220,115		—
Accrued interest receivable	29,375		29,375		—		29,375		—
Mortgage servicing rights, net	13,006		18,807		—		18,807		—
Net loans	4,126,655		4,139,777		—		4,062,688		77,089
Total financial assets	$	6,889,174	$	6,917,786	$	—	$	6,840,697	$	77,089
Financial liabilities:
Total deposits, excluding time deposits	$	4,684,664	$	4,684,664	$	—	$	4,684,664	$	—
Time deposits	1,343,681		1,351,742		—		1,351,742		—
Securities sold under repurchase agreements	467,205		467,205		—		467,205		—
Other borrowed funds	8		8		—		8		—
Accrued interest payable	6,433		6,433		—		6,433		—
Long-term debt	37,150		34,887		—		34,887		—
Subordinated debentures held by subsidiary    trusts	82,477		66,080		—		66,080		—
Total financial liabilities	$	6,621,618	$	6,611,019	$	—	$	6,611,019	$	—

					Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Carrying Amount		Estimated Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	$	801,332	$	801,332	$	—	$	801,332	$	—
Investment securities available-for-sale	1,995,258		1,995,258		—		1,995,258		—
Investment securities held-to-maturity	208,223		218,933		—		218,933		—
Accrued interest receivable	28,869		28,869		—		28,869		—
Mortgage servicing rights, net	12,653		16,373		—		16,373		—
Net loans	4,123,401		4,142,426		—		4,067,803		74,623
Total financial assets	$	7,169,736	$	7,203,191	$	—	$	7,128,568	$	74,623
Financial liabilities:
Total deposits, excluding time deposits	$	4,854,927	$	4,854,927	$	—	$	4,854,927	$	—
Time deposits	1,385,484		1,394,403		—		1,394,403		—
Securities sold under repurchase agreements	505,785		505,785		—		505,785		—
Other borrowed funds	32		32		—		32		—
Accrued interest payable	6,502		6,502		—		6,502		—
Long-term debt	37,160		35,104		—		35,104		—
Preferred stock pending redemption	50,000		50,000				50,000
Subordinated debentures held by subsidiary    trusts	82,477		62,409		—		62,409		—
Total financial liabilities	$	6,922,367	$	6,909,162	$	—	$	6,909,162	$	—

27

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS

(Dollars in thousands, except share and per share data)

(14) Recent Authoritative Accounting Guidance

ASU 2011-11, “Balance Sheet (Topic 210) - Disclosures about Offsetting Assets and Liabilities.” ASU 2011-11 amends Topic 210-Balance Sheet to require an entity to disclose both gross and net information about financial instruments that are eligible for offset in the statement of financial position and/or subject to a master netting arrangement or similar agreement. In January 2013, the Financial Accounting Standards Board, or FASB, issued ASU 2013-01, "Clarifying the Scope and Disclosures about Offsetting Assets and Liabilities," to clarify that the scope of ASU 2011-11 applies to derivatives accounted for in accordance with Topic 815, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset or subject to an enforceable master netting arrangement or similar agreement. ASU 2013-01 also clarifies that other types of financial assets and financial liabilities subject to a master netting arrangement or similar agreement are not subject to the provisions of ASU 2011-11. ASU 2011-11 and ASU 2013-01 became effective for the Company on January 1, 2013, and did not have a significant impact on the Company's consolidated financial statements, results of operations or liquidity.

ASU 2013-02 “Comprehensive Income (Topic 220) - Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income.” ASU 2013-02 requires entities to provide information about amounts reclassified out of accumulated other comprehensive income by component. The amendments in ASU 2013-02 require entities to present, either on the face of the income statement or in the notes significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income but only if the amount reclassified is required by U.S. GAAP to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income, entities are required to cross-reference to other disclosures required under U.S. GAAP that provide additional detail about those amounts. ASU 2013-02 became effective for the Company on January 1, 2013, and did not have a significant impact on the Company's consolidated financial statements, results of operations or liquidity.

ASU 2013-04 "Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date." ASU 2013-04 requires an entity to measure obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of (a) the amount the reporting entity agreed to pay on the basis of its arrangement among its co-obligors and (b) any additional amount the reporting entity expects to pay on behalf of its co-obligors. The amendments in ASU 2013-04 also requires an entity to disclose the nature, amount and other information about those obligations. ASU 2013-04 is effective for fiscal years, and interim period within those years, beginning after December 15, 2013, and is applied retrospectively to all prior periods presented. The Company does not expect amendments in ASU 2013-04 to impact the Company's consolidated financial statements, results of operations or liquidity.

(15) Subsequent Events

Subsequent events have been evaluated for potential recognition and disclosure through the date financial statements were filed with the Securities and Exchange Commission. On April 25, 2013, the Executive Committee of the Company's Board of Directors declared a quarterly dividend to common shareholders of $0.13 per share, to be paid on May 15, 2013 to shareholders of record as of May 6, 2013. No other events requiring recognition or disclosure were identified.

28

Item 2.

MANAGEMENT’S DISCUSSION AND ANALYSIS OF

FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2012, including the audited financial statements contained therein, filed with the Securities and Exchange Commission, or SEC.

When we refer to “we,” “our,” and “us” in this report, we mean First Interstate BancSystem, Inc. and our consolidated subsidiaries, unless the context indicates that we refer only to the parent company, First Interstate BancSystem, Inc.

Cautionary Note Regarding Forward-Looking Statements and Factors that Could Affect Future Results

This report contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, and Rule 175 promulgated thereunder, and Section 21E of the Securities Exchange Act of 1934, as amended, and Rule 3b-6 promulgated thereunder, that involve inherent risks and uncertainties. Any statements about our plans, objectives, expectations, strategies, beliefs, or future performance or events constitute forward-looking statements. Such statements are identified as those that include words or phrases such as “believes,” “expects,” “anticipates,” “plans,” “trend,” “objective,” “continue” or similar expressions or future or conditional verbs such as “will,” “would,” “should,” “could,” “might,” “may” or similar expressions. Forward-looking statements involve known and unknown risks, uncertainties, assumptions, estimates and other important factors that could cause actual results to differ materially from any results, performance or events expressed or implied by such forward-looking statements. The following factors, among others, may cause actual results to differ materially from current expectations in the forward-looking statements, including those set forth in this press release: continuing or worsening economic conditions, adverse economic conditions affecting Montana, Wyoming and western South Dakota, credit losses, concentrations of real estate loans, commercial loan risk, adequacy of the allowance for loan losses, impairment of goodwill, changes in interest rates, access to low-cost funding sources, increases in deposit insurance premiums, repurchases of mortgage loans from or reimbursements to investors due to contractual or warranty breach, inability to grow business, governmental regulation and changes in regulatory, tax and accounting rules and interpretations, sweeping changes in regulation of financial institutions due to passage of the Dodd-Frank Act, changes in or noncompliance with governmental regulations, effects of recent legislative and regulatory efforts to stabilize financial markets, dependence on the Company’s management team, ability to attract and retain qualified employees, failure of technology, reliance on external vendors, inability to meet liquidity requirements, lack of acquisition candidates, failure to manage growth, competition, inability to manage risks in turbulent and dynamic market conditions, ineffective internal operational controls, environmental remediation and other costs, litigation pertaining to fiduciary responsibilities, failure to effectively implement technology-driven products and services, capital required to support the Company’s bank subsidiary, soundness of other financial institutions, impact of proposed Basel III capital standards for U.S. banks, inability of our bank subsidiary to pay dividends, implementation of new lines of business or new product or service offerings, change in dividend policy, lack of public market for our Class A common stock, volatility of Class A common stock, voting control of Class B stockholders, decline in market price of Class A common stock, dilution as a result of future equity issuances, uninsured nature of any investment in Class A common stock, anti-takeover provisions, controlled company status and subordination of common stock to Company debt.

A more detailed discussion of each of the foregoing risks is included in the Company's Annual Report on Form 10-K for the year ended December 31, 2012, filed March 1, 2013. These factors and the other risk factors described in the Company's periodic and current reports filed with the SEC from time to time, however, are not necessarily all of the important factors that could cause the Company's actual results, performance or achievements to differ materially from those expressed in or implied by any of the Company's forward-looking statements. Other unknown or unpredictable factors also could harm the Company's results. Investors and others are encouraged to read the more detailed discussion of the Company's risks contained in the Company's Annual Report on Form 10-K for the year ended December 31, 2012.

All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by the cautionary statements set forth above. Forward-looking statements speak only as of the date they are made and we do not undertake or assume any obligation to update publicly any of these statements to reflect actual results, new information or future events, changes in assumptions or changes in other factors affecting forward-looking statements, except to the extent required by applicable laws. If we update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

29

Executive Overview

We are a financial and bank holding company headquartered in Billings, Montana. As of March 31, 2013, we had consolidated assets of $7,439 million, deposits of $6,028 million, loans of $4,225 million and total stockholders’ equity of $771 million. We currently operate 76 banking offices, including detached drive-up facilities, in 42 communities located in Montana, Wyoming and western South Dakota. Through the Bank, we deliver a comprehensive range of banking products and services to individuals, businesses, municipalities and other entities throughout our market areas. Our customers participate in a wide variety of industries, including energy, tourism, agriculture, healthcare, professional services, education, governmental services, construction, mining, retail and wholesale trade.

Our Business

Our principal business activity is lending to and accepting deposits from individuals, businesses, municipalities and other entities. We derive our income principally from interest charged on loans and, to a lesser extent, from interest and dividends earned on investments. We also derive income from non-interest sources such as fees received in connection with various lending and deposit services; trust, employee benefit, investment and insurance services; mortgage loan originations, sales and servicing; merchant and electronic banking services; and from time to time, gains on sales of assets. Our principal expenses include interest expense on deposits and borrowings, operating expenses, provisions for loan losses and income tax expense.

Our loan portfolio consists of a mix of real estate, consumer, commercial, agricultural and other loans, including fixed and variable rate loans. Our real estate loans comprise commercial real estate, construction (including residential, commercial and land development loans), residential, agricultural and other real estate loans. Fluctuations in the loan portfolio are directly related to the economies of the communities we serve. While each loan originated generally must meet minimum underwriting standards established in our credit policies, lending officers are granted discretion within pre-approved limits in approving and pricing loans to assure that the banking offices are responsive to competitive issues and community needs in each market area. We fund our loan portfolio primarily with the core deposits from our customers, generally without utilizing brokered deposits and with minimal reliance on wholesale funding sources.

Recent Trends and Developments

Asset Quality

Non-performing assets decreased to $133 million, or 3.12% of total loans and OREO, as of March 31, 2013, as compared to $143 million, or 3.35% of total loans and OREO as of December 31, 2012, primarily due to the movement of non-accrual loans out of the loan portfolio through charge-off or foreclosure.

The provision for loan losses decreased to $500 thousand for the three months ended March 31, 2013, as compared to $8.0 million for the three months ended December 31, 2012 and $11.3 million for three months ended March 31, 2012. These decreases are reflective of improvement in local and national economic trends, continued improvement in and stabilization of credit quality as evidenced by continuing declining levels of non-performing and criticized loans and high levels of recoveries of previously charged-off loans.

As of January 1, 2013, we no longer present accruing loans modified in troubled debt restructurings as non-performing loans. While still considered impaired under applicable accounting guidance, these loans are performing as agreed under their modified terms and management expects performance to continue. Prior period balances and ratios have been adjusted to reflect this change.

Primary Factors Used in Evaluating Our Business

As a banking institution, we manage and evaluate various aspects of both our financial condition and our results of operations. We monitor our financial condition and performance on a monthly basis, at our holding company, at the Bank and at each banking office. We evaluate the levels and trends of the line items included in our balance sheet and statements of income, as well as various financial ratios that are commonly used in our industry. We analyze these ratios and financial trends against both our own historical levels and the financial condition and performance of comparable banking institutions in our region and nationally.

Results of Operations

Principal factors used in managing and evaluating our results of operations include return on average assets, net interest income, non-interest income, non-interest expense and net income. Net interest income is affected by the level of interest rates, changes in interest rates and changes in the volume and composition of interest earning assets and interest bearing liabilities. The most significant impact on our net interest income between periods is derived from the interaction of changes in the rates

30

earned or paid on interest earning assets and interest bearing liabilities, which we refer to as interest rate spread. The volume of loans, investment securities and other interest earning assets, compared to the volume of interest bearing deposits and indebtedness, combined with the interest rate spread, produces changes in our net interest income between periods. Non-interest bearing sources of funds, such as demand deposits and stockholders’ equity, also support earning assets. The impact of free funding sources is captured in the net interest margin, which is calculated as net interest income divided by average earning assets. We evaluate our net interest income on factors that include the yields on our loans and other earning assets, the costs of our deposits and other funding sources, the levels of our net interest spread and net interest margin and the provisions for loan losses required to maintain our allowance for loan losses at an adequate level.

We seek to increase our non-interest income over time and we evaluate our non-interest income relative to the trends of the individual types of non-interest income in view of prevailing market conditions.

We manage our non-interest expenses in consideration of growth opportunities and our community banking model that emphasizes customer service and responsiveness. We evaluate our non-interest expense on factors that include our non-interest expense relative to our average assets, our efficiency ratio and the trends of the individual categories of non-interest expense.

Finally, we seek to increase our net income and provide favorable shareholder returns over time, and we evaluate our net income relative to the performance of other bank holding companies on factors that include return on average assets, return on average equity, total shareholder return and growth in earnings.

Financial Condition

Principal areas of focus in managing and evaluating our financial condition include liquidity, the diversification and quality of our loans, the adequacy of our allowance for loan losses, the diversification and terms of our deposits and other funding sources, the re-pricing characteristics and maturities of our assets and liabilities, including potential interest rate exposure and the adequacy of our capital levels. We seek to maintain sufficient levels of cash and investment securities to meet potential payment and funding obligations, and we evaluate our liquidity on factors that include the levels of cash and highly liquid assets relative to our liabilities, the quality and maturities of our investment securities, the ratio of loans to deposits and any reliance on brokered certificates of deposit or other wholesale funding sources.

We seek to maintain a diverse and high quality loan portfolio and evaluate our asset quality on factors that include the allocation of our loans among loan types, credit exposure to any single borrower or industry type, non-performing assets as a percentage of total loans and OREO, and loan charge-offs as a percentage of average loans. We seek to maintain our allowance for loan losses at a level adequate to absorb probable losses inherent in our loan portfolio at each balance sheet date, and we evaluate the level of our allowance for loan losses relative to our overall loan portfolio and the level of non-performing loans and potential charge-offs.

We seek to fund our assets primarily using core customer deposits spread among various deposit categories, and we evaluate our deposit and funding mix on factors that include the allocation of our deposits among deposit types, the level of our non-interest bearing deposits, the ratio of our core deposits (i.e. excluding time deposits above $100,000) to our total deposits and our reliance on brokered deposits or other wholesale funding sources, such as borrowings from other banks or agencies. We seek to manage the mix, maturities and re-pricing characteristics of our assets and liabilities to maintain relative stability of our net interest rate margin in a changing interest rate environment, and we evaluate our asset-liability management using models to evaluate the changes to our net interest income under different interest rate scenarios.

Finally, we seek to maintain adequate capital levels to absorb unforeseen operating losses and to help support the growth of our balance sheet. We evaluate our capital adequacy using the regulatory and financial capital ratios including leverage capital ratio, tier 1 risk-based capital ratio, total risk-based capital ratio, tangible common equity to tangible assets and tier 1 common capital to total risk-weighted assets.

Critical Accounting Estimates and Significant Accounting Policies

Our consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States and follow general practices within the industries in which we operate. Application of these principles requires management to make estimates, assumptions and judgments that affect the amounts reported in the consolidated financial statements and accompanying notes. The most significant accounting policies we follow are summarized in Notes 1 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2012.

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Our critical accounting estimates are summarized below. Management considers an accounting estimate to be critical if: (1) the accounting estimate requires management to make particularly difficult, subjective and/or complex judgments about matters that are inherently uncertain and (2) changes in the estimate that are reasonably likely to occur from period to period, or the use of different estimates that management could have reasonably used in the current period, would have a material impact on our consolidated financial statements, results of operations or liquidity.

Allowance for Loan Losses

The provision for loan losses creates an allowance for loan losses known and inherent in the loan portfolio at each balance sheet date. The allowance for loan losses represents management’s estimate of probable credit losses inherent in the loan portfolio.

We perform a quarterly assessment of the risks inherent in our loan portfolio, as well as a detailed review of each significant loan with identified weaknesses. Based on this analysis, we record a provision for loan losses in order to maintain the allowance for loan losses at appropriate levels. In determining the allowance for loan losses, we estimate losses on specific loans, or groups of loans, where the probable loss can be identified and reasonably determined. Determining the amount of the allowance for loan losses is considered a critical accounting estimate because it requires significant judgment and the use of subjective measurements, including management’s assessment of the internal risk classifications of loans, historical loan loss rates, changes in the nature of the loan portfolio, overall portfolio quality, industry concentrations, delinquency trends and the impact of current local, regional and national economic factors on the quality of the loan portfolio. Changes in these estimates and assumptions are possible and may have a material impact on our allowance, and therefore our consolidated financial statements or results of operations. The allowance for loan losses is maintained at an amount we believe is sufficient to provide for estimated losses inherent in our loan portfolio at each balance sheet date, and fluctuations in the provision for loan losses result from management’s assessment of the adequacy of the allowance for loan losses. Management monitors qualitative and quantitative trends in the loan portfolio, including changes in the levels of past due, internally classified and non-performing loans. Note 1 of the Notes to Consolidated Financial Statements in our Annual Report on Form 10-K for the year ended December 31, 2012 describes the methodology used to determine the allowance for loan losses. A discussion of the factors driving changes in the amount of the allowance for loan losses is included herein under the heading “Asset Quality."

Goodwill

The excess purchase price over the fair value of net assets from acquisitions, or goodwill, is evaluated for impairment at least annually and on an interim basis if an event or circumstance indicates that it is likely impairment has occurred. In any given year, the Company may elect to perform a qualitative assessment to determine whether it is more likely than not that the fair value of a reporting unit is in excess of its carrying value. If it is not more likely than not that the fair value of the reporting unit is in excess of the carrying value, or if the Company elects to bypass the qualitative assessment, a two-step quantitative impairment test is performed. In performing a quantitative test for impairment, the fair value of net assets is estimated based on an analysis of our market value, discounted cash flows and peer values. Determining the fair value of goodwill is considered a critical accounting estimate because of its sensitivity to market-based economics. In addition, any allocation of the fair value of goodwill to assets and liabilities requires significant management judgment and the use of subjective measurements. Variability in market conditions and key assumptions or subjective measurements used to estimate and allocate fair value are reasonably possible and could have a material impact on our consolidated financial statements or results of operations. Note 1 of the Notes to the Consolidated Financial Statements in our Annual Report on Form 10-K for the year ended December 31, 2012 describes our accounting policy with regard to goodwill.

Our annual evaluation of goodwill for impairment performed as of July 1st each year. Upon completion of the most recent evaluation, it was determined that the estimated fair value of net assets was greater than carrying value of the Company. We will continue to monitor our performance and evaluate our goodwill for impairment annually or more frequently as needed.

Results of Operations

The following discussion and analysis is intended to provide greater details of the results of our operations and financial condition.

Net Interest Income. During first quarter 2013, our net interest income on a fully-taxable equivalent, or FTE, basis decreased $1.7 million, or 2.8%, to $60.4 million, as compared to $62.1 million during fourth quarter 2012, and $1.4 million, or 2.2%, from $61.8 million during first quarter 2012. Declines in yields earned on our loan and investment portfolios during first quarter 2013 were partially offset by increases in average outstanding loans and investment securities, reductions in the cost of interest bearing liabilities and, compared to fourth quarter 2012, lower average outstanding interest bearing deposits in banks. Also offsetting the impact of lower asset yields was an approximate 150 basis point decrease in the cost of our junior subordinated

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debentures during first quarter 2013, as compared to fourth quarter 2012 and first quarter 2012, due to the contractual repricing of $46 million of junior subordinated debentures from fixed interest rates to variable rates priced from 2.40% to 2.75% over LIBOR.

Our net interest margin ratio, on a fully taxable-equivalent, or FTE, basis, remained flat at 3.55% for the three months ended March 31, 2013, as compared to the three months ended December 31 2012, and decreased 17 basis points from 3.72% for the the three months ended March 31, 2012. Impacting our net FTE interest margin ratio were net recoveries of charged-off interest. During first quarter 2013, we recorded net recoveries of charged-off interest of $620 thousand, as compared to net recoveries of $425 thousand during fourth quarter 2012 and net charged-off interest of $94 thousand during first quarter 2012. Exclusive of net recoveries of charged-off interest, our net interest margin ratio was 3.51% for the three months ended March 31, 2013, 3.53% for the three months ended December 31, 2012, and 3.72% for the three months ended March 31, 2012.

The following table presents, for the periods indicated, condensed average balance sheet information, together with interest income and yields earned on average interest earning assets and interest expense and rates paid on average interest bearing liabilities.

Average Balance Sheets, Yields and Rates
(Dollars in thousands)	Three Months Ended March 31,
	2013							2012
	Average Balance		Interest			Average Rate		Average Balance		Interest			Average Rate
Interest earning assets:
Loans (1) (2)	$	4,216,934	$	55,913		5.38	%	$	4,165,203	$	58,374		5.64	%
Investment securities (2)	2,204,458		9,980			1.84		2,143,438		11,604			2.18
Interest bearing deposits in banks	476,856		298			0.25		374,899		237			0.25
Federal funds sold	2,521		4			0.64		609		1			0.66
Total interest earnings assets	6,900,769		66,195			3.89		6,684,149		70,216			4.23
Non-earning assets	598,283							619,137
Total assets	$	7,499,052						$	7,303,286
Interest bearing liabilities:
Demand deposits	$	1,728,813	$	473		0.11	%	$	1,582,805	$	646		0.16	%
Savings deposits	1,550,146		653			0.17		1,449,239		1,015			0.28
Time deposits	1,365,232		3,229			0.96		1,540,789		4,601			1.20
Repurchase agreements	512,180		100			0.08		513,407		156			0.12
Other borrowed funds	7		—			—		35		—			—
Preferred stock pending redemption	9,444		159			6.83		—		—			—
Long-term debt	37,153		480			5.24		37,194		498			5.39
Subordinated debentures held by by subsidiary trusts	82,477		696			3.42		123,715		1,507			4.90
Total interest bearing liabilities	5,285,452		5,790			0.44		5,247,184		8,423			0.65
Non-interest bearing deposits	1,398,850							1,232,874
Other non-interest bearing liabilities	53,810							50,071
Stockholders’ equity	$	760,940						$	773,157
Total liabilities and stockholders’ equity	7,499,052							7,303,286
Net FTE interest income			60,405							61,793
Less FTE adjustments (2)			$	(1,128	)					$	(1,159	)
Net interest income from consolidated statements of income			59,277							60,634
Interest rate spread						3.45	%						3.58	%
Net FTE interest margin (3)						3.55	%						3.72	%
Cost of funds, including non-interest bearing demand deposits (4)						0.35	%						0.52	%

(1) Average loan balances include non-accrual loans. Interest income on loans includes amortization of deferred loan fees net of deferred loan costs, which is not material.

(2) Interest income and average rates for tax exempt loans and securities are presented on a FTE basis.

(3) Net FTE interest margin during the period equals (i) the difference between annualized interest income on interest earning assets and the annualized interest expense on interest bearing liabilities, divided by (ii) average interest earning assets for the period.

(4) Calculated by dividing total annualized interest on interest bearing liabilities by the sum of total interest bearing liabilities plus non-interest bearing deposits.

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The table below sets forth, for the periods indicated, a summary of the changes in interest income and interest expense resulting from estimated changes in average asset and liability balances (volume) and estimated changes in average interest rates (rate). Changes which are not due solely to volume or rate have been allocated to these categories based on the respective percent changes in average volume and average rate as they compare to each other.

Analysis of Interest Changes Due to Volume and Rates
(Dollars in thousands)	Three Months Ended March 31, 2013 compared with Three Months Ended March 31, 2012
	Volume			Rate			Net
Interest earning assets:
Loans (1)	$	725		$	(3,186	)	$	(2,461	)
Investment securities (1)	330			(1,954		)	(1,624		)
Interest bearing deposits in banks	64			(3		)	61
Federal funds sold	3			—			3
Total change	1,122			(5,143		)	(4,021		)
Interest bearing liabilities:
Demand deposits	60			(233		)	(173		)
Savings deposits	71			(433		)	(362		)
Time deposits	(524		)	(848		)	(1,372		)
Repurchase agreements	—			(56		)	(56		)
Long-term debt	(1		)	(17		)	(18		)
Preferred stock pending redemption	159			—			159
Subordinated debentures	(502		)	(309		)	(811		)
Total change	(737		)	(1,896		)	(2,633		)
Increase (decrease) in FTE net interest income	$	1,859		$	(3,247	)	$	(1,388	)

(1)Interest income for tax exempt loans and securities are presented on a FTE basis.

Provision for Loan Losses. The provision for loan losses decreased $10.8 million, or 95.6%, to $500 thousand for the three months ended March 31, 2013, as compared to $11.3 million for the same period in 2012, and decreased $7.5 million, or 93.8%, as compared to $8.0 million during the three months ended December 31, 2012. Decreases in the provision for loan losses are reflective of improvement in local and national economic trends, continued improvement in and stabilization of credit quality as evidenced by declining levels of non-performing and criticized loans and a high level of recoveries of previously charged-off loans. For information regarding our non-performing loans, see “Non-Performing Assets” included herein.

Non-interest Income. Our principal sources of non-interest income include other service charges, commissions and fees; income from the origination and sale of loans; service charges on deposit accounts; and, wealth management revenues. Non-interest income increased $2.4 million, or 9.2%, to $28.8 million for the three months ended March 31, 2013, as compared to $26.4 million for the same period in 2012, and decreased $1.8 million, or 5.9%, as compared to $30.6 million during the three months ended December 31, 2012. Significant components of these fluctuations are discussed below.

Fluctuations in market interest rates have a significant impact on the level of income from the origination and sale of loans. Income from the origination and sale of loans increased $2.3 million, or 27.3%, to $10.7 million during the three months ended March 31, 2013, as compared to $8.4 million during the same period in 2012, and decreased $1.6 million, or 13.4%, as compared to $12.3 million during the three months ended December 31, 2012. Loans originated for purchased homes were approximately $105 million during first quarter 2013, the highest first quarter level in the Company's history and a 24.9% increase from first quarter 2012. Loans originated for purchased homes are less sensitive to changes in market interest rates than loans originated to refinance existing mortgages. Loans originated for purchased homes accounted for approximately 33% of our first quarter 2013 residential loan origination, compared to 32% during fourth quarter 2012, and 29% during first quarter 2012.

Other service charges, commissions and fees primarily include debit and credit card interchange income, mortgage servicing fees, insurance and other commissions and ATM service charge revenues. Other service charges, commissions and fees decreased $168 thousand, or 2.0%, to $8.3 million during the three months ended March 31, 2013, as compared to $8.4 million during the same period in the prior year, and $518 thousand, or 5.9%, as compared to $8.8 million during the three months

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ended December 31, 2012. Decreases in other service charges, commissions and fees during first quarter 2013, as compared to fourth quarter 2012, were primarily due to lower credit and debit card transaction volumes that typically occur during the first quarter of each year.

Wealth management revenues are comprised principally of fees earned for management of trust assets and investment services revenues. Fees earned for management of trust assets are generally based on the market value of assets managed. Wealth management revenues increased $851 thousand, or 25.9%, to $4.1 million during the three months ended March 31, 2013, as compared to $3.3 million during the same period in 2012, and increased $475 thousand, or 13.0%, as compared to $3.7 million during the three months ended December 31, 2012, primarily due to the addition of new wealth management customers and increases in the market values of new and existing assets under trust management.

Other income decreased $421 thousand, or 20.1%, to $1.7 million for the three months ended March 31, 2013, compared to $2.1 million for the same period in 2012, and increased $251 thousand, or 17.6%, as compared to $1.4 million during the three months ended December 31, 2012. Variations in other income between periods were primarily due to fluctuations in earnings on securities held under deferred compensation plans.

Non-interest Expense. Non-interest expense decreased $755 thousand, or 1.3%, to $56.7 million for the three months ended March 31, 2013, as compared to $57.4 million for the same period in 2012, and decreased $1.1 million, or 2.0%, as compared to $57.8 million for the three months ended December 31, 2012. Significant components of these decreases are discussed below.

Salaries and wages increased $1.8 million, or 8.5%, to $23.4 million during the three months ended March 31, 2013, as compared to $21.6 million during the same period in the prior year, and increased $117 thousand , or less than 1%, as compared to $23.3 million during the three months ended December 31, 2012, primarily due to higher incentive compensation accruals reflective of our improved financial performance. Increases in incentive compensation accruals during first quarter 2013, as compared to fourth quarter 2012, were largely offset by a reduction in salaries expense due to a slight decrease in full-time equivalent employees.

Employee benefits expense decreased $791 thousand, or 8.8%, to $8.2 million during the three months ended March 31, 2013, as compared to $9.0 million during same period in 2012, primarily due to lower discretionary profit sharing accruals. Employee benefits expense increased $2.1 million, or 33.7%, as compared to $6.1 million during the three months ended December 31, 2012, due to the fourth quarter 2012 reversal of $1.1 million of previously accrued group health insurance expense to reflect favorable claims experience in 2012. Also contributing to the increase in employees benefits expense during first quarter 2013, as compared to fourth quarter 2012, were payroll tax and stock-based compensation expenses.

OREO expense is recorded net of OREO income. Variations in net OREO expense between periods were primarily due to fluctuations in write-downs of the estimated fair value of OREO properties, net gains and losses recorded on the sales of OREO properties and carrying costs and/or operating expenses of OREO properties. OREO expense, net of income, increased $791 thousand, or 71.6%, to $1.9 million for the three months ended March 31, 2013, as compared to $1.1 million for the same period in 2012, and decreased $2.0 million, or 51.1%, as compared to $3.9 million during the three months ended December 31, 2012. First quarter 2013 net OREO expense included $411 thousand of net operating expenses, $2.3 million of fair value write-downs and net gains of $820 thousand on the sale of OREO properties, as compared to $453 thousand of net operating expenses, $578 thousand of fair value write-downs and net losses of $74 thousand during first quarter 2012 and $883 thousand of net operating expenses, $3.3 million of fair value write-downs and net gains of $273 thousand during fourth quarter 2012.

Other expenses primarily include advertising and public relations costs; office supply, postage, freight and telephone expenses; travel expense; donations expense; debit and credit card expenses; board of director fees; and other losses. Other expenses decreased $3.2 million, or 23.5%, to $10.3 million for the three months ended March 31, 2013, as compared to $13.5 million during the same period in the prior year, due to the first quarter 2012 accrual of $3.0 million of collection and settlement costs related to one borrower. Other expenses decreased $795 thousand, or 7.1%, to $10.3 million for the three months ended March 31, 2013, as compared to $11.1 million for the three months ended December 31, 2012, primarily due to lower advertising expense due to differences in the timing of advertising campaigns.     

Mortgage servicing rights are evaluated quarterly for impairment. Fluctuations in the fair value of mortgage servicing rights are primarily due to changes in assumptions regarding prepayments of the underlying mortgage loans, which typically correspond with changes in market interest rates. During the three months ended March 31, 2013, we reversed impairment of mortgage servicing rights of $48 thousand, as compared to a reversal of impairment of $868 thousand during the same period in the prior year, and the reversal of impairment of $10 thousand during the three months ended December 31, 2012.

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Income Tax Expense. Our effective federal income tax rate was 30.8% for the three months ended March 31, 2013 and 28.7% for the three months ended March 31, 2012. Changes in the effective federal income tax rates were primarily due to higher levels of taxable income without a proportional increase in tax exempt interest income on loan and investment securities.

State income tax applies primarily to pretax earnings generated within Montana and South Dakota. Our effective state tax rate was 4.4% for the three months ended March 31, 2013 and 4.6% for the three months ended March 31, 2012.

Financial Condition

Total assets decreased $282 million, or 3.7%, to $7,439 million as of March 31, 2013, from $7,722 million as of December 31, 2012.

Loans. Total loans increased $647 thousand, or less than 1%, to $4,225 million as of March 31, 2013, from $4,224 million as of December 31, 2012. All major loan categories decreased or remained flat with the exception of residential real estate and indirect consumer loans. Residential real estate loans increased to $758 million as of March 31, 2013, from $708 million as of December 31, 2012, due to retention of certain residential loans with contractual maturities of fifteen years or less. Indirect consumer loans grew to $444 million as of March 31, 2013, from $438 million as of December 31, 2012, due to continuing expansion of our indirect lending program within our existing market areas and competitive loan pricing.

The most significant decreases in total loans as of March 31, 2013, as compared to December 31, 2012, occurred in commercial real estate and real estate construction loans. Commercial real estate loans decreased $28 million, or 1.9%, to $1,469 million as of March 31, 2013, from $1,497 million as of December 31, 2012, primarily due to slow loan growth combined with the movement of lower quality loans out of the portfolio through charge-off, pay-off and foreclosure. Real estate construction loans decreased $4 million, or 1.1%, to $331 million as of March 31, 2013, from $335 million as of December 31, 2012. Decreases in real estate construction loans occurred primarily in land acquisition and development loans and were largely due to movement of lower quality loans out of the portfolio through charge-off or foreclosure. In recent quarters, real estate construction loans outstanding have begun to stabilize due to increased housing construction in our market areas.

Non-performing Assets. Non-performing assets include non-accrual loans, loans contractually past due 90 days or more and still accruing interest and OREO. The following table sets forth information regarding non-performing assets as of the dates indicated:

Nonperforming Assets
(Dollars in thousands)	March 31, 2013			December 31, 2012			September 30, 2012			June 30, 2012			March 31, 2012
Non-performing loans:
Non-accrual loans	$	98,594		$	107,799		$	122,931		$	129,923		$	180,910
Accruing loans past due 90 days or more	1,941			2,277			4,339			6,451			5,017
Total non-performing loans	100,535			110,076			127,270			136,374			185,927
OREO	32,470			32,571			39,971			53,817			44,756
Total non-performing assets	$	133,005		$	142,647		$	167,241		$	190,191		$	230,683
Non-performing loans to total loans	2.38		%	2.61		%	3.04		%	3.27		%	4.47		%
Non-performing assets to total loans and OREO	3.12		%	3.35		%	3.96		%	4.50		%	5.49		%
Non-performing assets to total assets	1.79		%	1.85		%	2.24		%	2.60		%	3.12		%

Non-performing loans. Non-performing loans include non-accrual loans and loans contractually past due 90 days or more. We monitor and evaluate collateral values on non-performing loans quarterly. Appraisals are required on all non-performing loans every 18-24 months, or sooner as conditions necessitate. We monitor real estate values by market for our larger market areas. Based on trends in real estate values, adjustments may be made to the appraised value based on time elapsed between the appraisal date and the impairment analysis or a new appraisal may be ordered. Appraised values in our smaller market areas may be adjusted based on trends identified through discussions with local realtors and appraisers. Appraisals are also adjusted for selling costs. The adjusted appraised value is then compared to the loan balance and any resulting shortfall is recorded in the allowance for loan losses as a specific valuation allowance. Overall increases in specific valuation allowances will result in higher provisions for loan losses. Provisions for loan losses are also impacted by changes in the historical or general valuation elements of the allowance for loan losses as well.

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The following table sets forth the allocation of our non-performing loans among our various loan categories as of the dates indicated:

Non-Performing Loans by Loan Type
(Dollars in thousands)	March 31, 2013		Percent of Total		December 31, 2012		Percent of Total
Real estate:
Commercial	$	44,951	44.7	%	$	50,517	45.8	%
Construction:			.
Land acquisition and development	16,773		16.8	%	19,628		17.8	%
Commercial	6,483		6.4	%	8,126		7.4	%
Residential	1,336		1.3	%	2,175		2.0	%
Total construction	24,592		24.5	%	29,929		27.2	%
Residential	9,601		9.5	%	11,511		10.5	%
Agricultural	4,593		4.6	%	5,048		4.6	%
Total real estate	83,737		83.3	%	97,005		88.1	%
Consumer	1,666		1.7	%	1,727		1.6	%
Commercial	14,897		14.8	%	10,812		9.8	%
Agricultural	235		0.2	%	525		0.5	%
Other	—		—	%	7		—	%
Total non-performing loans	$	100,535	100.0	%	$	110,076	100.0	%

Non-accrual loans. We generally place loans on non-accrual when they become 90 days past due, unless they are well secured and in the process of collection. When a loan is placed on non-accrual status, any interest previously accrued but not collected is reversed from income. If all loans on non-accrual had been current in accordance with their original terms, gross income of approximately $1.4 million and $2.7 million would have been accrued for the three months ended March 31, 2013 and 2012, respectively.

Non-accrual loans, the largest component of non-performing loans, decreased $9  million, or 8.5%, to $99 million at March 31, 2013, from $108 million at December 31, 2012, primarily due to movement of non-accrual loans out of the loan portfolio through charge-off and foreclosure.

OREO. OREO consists of real property acquired through foreclosure on the collateral underlying defaulted loans. We initially record OREO at fair value less estimated selling costs. Any excess of loan carrying value over the fair value of the real estate acquired is recorded as charge against the allowance for loan losses. Estimated losses that result from the ongoing periodic valuation of these properties are charged to earnings in the period in which they are identified. The fair values of OREO properties are estimated using appraisals and management estimates of current market conditions. OREO properties are appraised every 18-24 months unless deterioration in local market conditions indicates the need to obtain new appraisals sooner. OREO properties are evaluated by management quarterly to determine if additional write-downs are appropriate or necessary based on current market conditions. Quarterly evaluations include a review of the most recent appraisal of the property and reviews of recent appraisals and comparable sales data for similar properties in the same or adjacent market areas. Commercial and agricultural OREO properties are listed with unrelated third party professional real estate agents or brokers local to the areas where the marketed properties are located. Residential properties are typically listed with local realtors, after any redemption period has expired. We rely on these local real estate agents and/or brokers to list the properties on the local multiple listing system, to provide marketing materials and advertisements for the properties and to conduct open houses.

OREO remained relatively unchanged at $32 million as of March 31, 2013 and December 31, 2012. During the three months ended March 31, 2013, we recorded additions to OREO of $5 million, wrote down the fair value of OREO properties by $2 million and sold OREO with a book value of $3 million at a gain of $820 thousand. As of March 31, 2013, the composition of our OREO was as follows: 41% land and land development properties, 32% commercial properties and 27% residential properties.

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Allowance for Loan Losses. The Company performs a quarterly assessment of the adequacy of its allowance for loan losses in accordance with generally accepted accounting principles. The methodology used to assess the adequacy is consistently applied to the Company's loan portfolio. The allowance for loan losses is established through a provision for loan losses based on our evaluation of known and inherent risk in our loan portfolio at each balance sheet date. In determining the allowance for loan losses, we estimate losses on specific loans, or groups of loans, where the probable loss can be identified and reasonably determined. The balance of the allowance for loan losses is based on internally assigned risk classifications of loans, historical loan loss rates, changes in the nature of the loan portfolio, overall portfolio quality, industry concentrations, delinquency trends, current economic factors and the estimated impact of current economic conditions on certain historical loan loss rates. See the discussion under “Critical Accounting Estimates and Significant Accounting Policies — Allowance for Loan Losses” above.

The allowance for loan losses is increased by provisions charged against earnings and reduced by net loan charge-offs. Loans, or portions thereof, are charged-off when management believes that the collectibility of the principal is unlikely or, with respect to consumer installment and credit card loans, according to established delinquency schedules.

The allowance for loan losses consists of three elements:

(1) Specific valuation allowances associated with impaired loans. Specific valuation allowances are determined based on assessment of the fair value of the collateral underlying the loans as determined through independent appraisals, the present value of future cash flows, observable market prices and any relevant qualitative or environmental factors impacting the loan. No specific valuation allowances are recorded for impaired loans that are adequately secured.

(2) Historical valuation allowances based on loan loss experience for similar loans with similar characteristics and trends. Historical valuation allowances are determined by applying percentage loss factors to the credit exposures from outstanding loans. For commercial, agricultural and real estate loans, loss factors are applied based on the internal risk classifications of these loans. For consumer loans, loss factors are applied on a portfolio basis. For commercial, agriculture and real estate loans, loss factor percentages are based on a migration analysis of our historical loss experience, designed to account for credit deterioration. For consumer loans, loss factor percentages are based on a one-year loss history.

(3) General valuation allowances determined based on changes in the nature of the loan portfolio, overall portfolio quality, industry concentrations, delinquency trends, general economic conditions and other qualitative risk factors both internal and external to us.

Based on the assessment of the adequacy of the allowance for loan losses, management records provisions for loan losses to maintain the allowance for loan losses at appropriate levels.

Loans, or portions thereof, are charged-off against the allowance for loan losses when management believes that the collectability of the principal is unlikely, or, with respect to consumer installment loans, according to an established delinquency schedule. Generally, loans are charged-off when (1) there has been no material principal reduction within the previous 90 days and there is no pending sale of collateral or other assets, (2) there is no significant or pending event which will result in principal reduction within the upcoming 90 days, (3) it is clear that we will not be able to collect all or a portion of the loan, (4) payments on the loan are sporadic, will result in an excessive amortization or are not consistent with the collateral held and (5) foreclosure or repossession actions are pending. Loan charge-offs do not directly correspond with the receipt of independent appraisals or the use of observable market data if the collateral value is determined to be sufficient to repay the principal balance of the loan.

If the impaired loan is adequately collateralized, a specific valuation allowance is not recorded. As such, significant changes in impaired and non-performing loans do not necessarily correspond proportionally with changes in the specific valuation component of the allowance for loan losses. Additionally, management expects the timing of charge-offs will vary between quarters and will not necessarily correspond proportionally to changes in the allowance for loan losses or changes in non-performing or impaired loans due to timing differences among the initial identification of an impaired loan, recording of a specific valuation allowance for the impaired loan and any resulting charge-off of uncollectible principal.

38

The following table sets forth information regarding our allowance for loan losses as of and for the periods indicated.

Allowance for Loan Losses
(Dollars in thousands)	Three Months Ended
	March 31,			December 31,			September 30,			June 30,			March 31,
	2013			2012			2012			2012			2012
Balance at beginning of period	$	100,511		$	99,006		$	102,794		$	115,902		$	112,581
Provision charged to operating expense	500			8,000			9,500			12,000			11,250
Charge offs:
Real estate
Commercial	1,098			2,914			3,058			6,362			681
Construction	1,723			3,355			4,477			15,107			2,571
Residential	1,226			590			1,603			861			1,825
Agricultural	96			2			1			20			79
Consumer	1,062			1,458			1,340			1,210			1,312
Commercial	811			1,963			4,334			3,180			2,512
Agricultural	4			9			—			5			107
Total charge-offs	6,020			10,291			14,813			26,745			9,087
Recoveries:
Real estate
Commercial	714			318			24			483			213
Construction	325			1,443			260			13			173
Residential	23			59			102			30			120
Agricultural	1			—			2			—			—
Consumer	472			471			465			488			521
Commercial	1,375			1,504			665			609			126
Agricultural	3			1			7			14			5
Total recoveries	2,913			3,796			1,525			1,637			1,158
Net charge-offs	3,107			6,495			13,288			25,108			7,929
Balance at end of period	$	97,904		$	100,511		$	99,006		$	102,794		$	115,902
Period end loans	$	4,224,559		$	4,223,912		$	4,180,051		$	4,169,963		$	4,158,616
Average loans	4,216,934			4,197,665			4,183,016			4,159,565			4,165,203
Net loans charged-off to average loans, annualized	0.30		%	0.62		%	1.26		%	2.43		%	0.76		%
Allowance to period end loans	2.32		%	2.38		%	2.37		%	2.47		%	2.79		%

Although we believe that we have established our allowance for loan losses in accordance with accounting principles generally accepted in the United States and that the allowance for loan losses was adequate to provide for known and inherent losses in the portfolio at all times, future provisions will be subject to on-going evaluations of the risks in the loan portfolio. If the economy declines or asset quality deteriorates, material additional provisions could be required.

Investment Securities. We manage our investment portfolio to obtain the highest yield possible, while meeting our risk tolerance and liquidity guidelines and satisfying the pledging requirements for deposits of state and political subdivisions and securities sold under repurchase agreements. Investment securities increased $18 million, or less than 1%, to $2,222 million, or 30.0% of total assets, as of March 31, 2013, from $2,203 million, or 28.5% of total assets, as of December 31, 2012.         

We evaluate our investment portfolio quarterly for other-than-temporary declines in the market value of individual investment securities. This evaluation includes monitoring credit ratings; market, industry and corporate news; volatility in market prices; and, determining whether the market value of a security has been below its cost for an extended period of time. As of March 31, 2013, we had investment securities with fair values of $650 thousand that had been in a continuous loss position more than twelve months. Gross unrealized losses on these securities totaled $7 thousand as of March 31, 2013, and were attributable to changes in interest rates. No impairment losses were recorded during the three months ended March 31, 2013 and 2012.

39

Deposits. Our deposits consist of non-interest bearing and interest bearing demand, savings, individual retirement and time deposit accounts. Total deposits decreased $212 million, or 3.4%, to $6,028 million as of March 31, 2013, from $6,240 million December 31, 2012, with a slight shift in the mix of deposits away from demand and time deposits to savings deposits. Total deposits were at an historically high level as of December 31, 2012 and returned to a more normalized level as of March 31, 2013. Management attributes the decrease in total deposits as of March 31, 2013, compared to December 31, 2012, to a myriad of factors including customers reinvesting cash into stocks and other investments to take advantage of improvement in the stock market, business customers reinvesting cash into their own businesses and individual and corporate income tax payments.

The following table summarizes our deposits as of the dates indicated:

Deposits
(Dollars in thousands)	March 31, 2013		Percent of Total		December 31, 2012		Percent of Total
Non-interest bearing demand	$	1,406,892	23.3	%	$	1,495,309	24.0	%
Interest bearing:
Demand	1,713,715		28.4		1,811,905		29.0
Savings	1,564,057		26.0		1,547,713		24.8
Time, $100 and over	569,427		9.5		594,712		9.5
Time, other (1)	774,254		12.8		790,772		12.7
Total interest bearing	4,621,453		76.7		4,745,102		76.0
Total deposits	$	6,028,345	100.0	%	$	6,240,411	100.0	%

(1) Included in Time, other are Certificate of Deposit Account Registry Service, or CDAR, deposits of $69 million as of March 31, 2013 and $72 million as of December 31, 2012.

Repurchase Agreements. In addition to deposits, repurchase agreement with commercial depositors, which include municipalities, provide an additional source of funds. Under repurchase agreements, deposits balances are invested in short-term U.S. government agency securities overnight and are then repurchased the following day. All outstanding repurchase agreements are due in one day. Repurchase agreements decreased $39 million, or 7.6%, to $467 million as of March 31, 2013, from $506 million as of December 31, 2012, due to fluctuations in the liquidity of our customers.

Preferred Stock Redemption. On January 18, 2013, we redeemed $50 million of outstanding 6.75% Series A noncumulative redeemable preferred stock, or preferred stock. The aggregate redemption price was $50 million, which represented par value plus unpaid and accrued dividends to the date of redemption. The preferred stock was reclassified from stockholders' equity to a liability upon notice of the redemption to preferred stockholders in December 2012.

Capital Resources and Liquidity Management

Stockholders’ equity is influenced primarily by earnings, dividends, changes in the unrealized holding gains or losses, net of taxes, on available-for-sale investment securities and sales and redemptions of common stock. Stockholders’ equity increased $20 million, or 2.7%, to $771 million as of March 31, 2013, from $751 million as of December 31, 2012, due to the retention of earnings.

During fourth quarter 2012, we declared and paid an accelerated aggregate quarterly cash dividend of $5.6 million, or $0.13 per share, to common shareholders. This accelerated dividend, paid on December 17, 2013, was in lieu of the quarterly dividend which would have been declared and paid in January 2013. On April 25, 2013, we declared a quarterly dividend to common stockholders of $0.13 per share to be paid on May 15, 2013 to shareholders of record as of May 6, 2013.

Pursuant to the Federal Deposit Insurance Corporation Improvement Act, the Federal Reserve and FDIC have adopted regulations setting forth a five-tier system for measuring the capital adequacy of the financial institutions they supervise. As of March 31, 2013 and December 31, 2012, the Bank had capital levels that, in all cases, exceeded the well-capitalized guidelines. As of March 31, 2013, we had consolidated leverage, tier 1 and total risk-based capital ratios of 9.24%, 14.07% and 15.91%, respectively, as compared to 8.81%, 13.60% and 15.59%, respectively, as of December 31, 2012. For additional information regarding our capital levels see “Note 8 – Regulatory Capital” in the accompanying “Notes to Unaudited Consolidated Financial Statements” included in this report.

40

Liquidity. Liquidity measures our ability to meet current and future cash flow needs on a timely basis and at a reasonable cost. We manage our liquidity position to meet the daily cash flow needs of customers, while maintaining an appropriate balance between assets and liabilities to meet the return on investment objectives of our shareholders. Our liquidity position is supported by management of liquid assets and liabilities and access to alternative sources of funds. Liquid assets include cash, interest bearing deposits in banks, federal funds sold, available-for-sale investment securities and maturing or prepaying balances in our held-to-maturity investment and loan portfolios. Liquid liabilities include core deposits, federal funds purchased, securities sold under repurchase agreements and borrowings. Other sources of liquidity include the sale of loans, the ability to acquire additional national market, non-core deposits, the issuance of additional collateralized borrowings such as FHLB advances, the issuance of debt securities, additional borrowings through the Federal Reserve’s discount window and the issuance of preferred or common securities.

Our short-term and long-term liquidity requirements are primarily to fund on-going operations, including payment of interest on deposits and debt, extensions of credit to borrowers, capital expenditures and shareholder dividends. These liquidity requirements are met primarily through cash flow from operations, redeployment of prepaying and maturing balances in our loan and investment portfolios, debt financing and increases in customer deposits. For additional information regarding our operating, investing and financing cash flows, see the unaudited “Consolidated Statements of Cash Flows,” included in Part I, Item 1.

As a holding company, we are a corporation separate and apart from the Bank and, therefore, we provide for our own liquidity. Our main sources of funding include management fees and dividends declared and paid by the Bank and access to capital markets. There are statutory, regulatory and debt covenant limitations that affect the ability of our subsidiary bank to pay dividends to us. Management believes that such limitations will not impact our ability to meet our ongoing short-term cash obligations.

Management continuously monitors our liquidity position and adjustments are made to the balance between sources and uses of funds as deemed appropriate. Our management is not aware of any events that are reasonably likely to have a material adverse effect on our liquidity, capital resources or operations. In addition, our management is not aware of any regulatory recommendations regarding liquidity, which if implemented, would have a material adverse effect on us.

Recent Accounting Pronouncements

See “Note 14 – Recent Authoritative Accounting Guidance” in the accompanying “Notes to Unaudited Consolidated Financial Statements” included in this report for details of recently issued accounting pronouncements and their expected impact on our financial statements.    

Item 3.

QUANTITATIVE AND QUALITATIVE DISCLOSURES

ABOUT MARKET RISK

As of March 31, 2013, there have been no material changes in the quantitative and qualitative information about market risk provided pursuant to Item 305 of Regulation S-K as presented in our Annual Report on Form 10-K for the year ended December 31, 2012.

Item 4.

CONTROLS AND PROCEDURES

Disclosure Controls and Procedures

Our management is responsible for establishing and maintaining effective disclosure controls and procedures, as defined under Rules 13a-15(e) and 15d-15(e) of the Exchange Act. As of March 31, 2013, an evaluation was performed, under the supervision and with the participation of management, including the Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of our disclosure controls and procedures. Based on that evaluation, the Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures as of March 31, 2013, were effective in ensuring that information required to be disclosed in our reports filed or submitted under the Exchange Act is recorded, processed, summarized, and reported within the time periods required by the SEC’s rules and forms, and is accumulated and communicated to our management, including our Chief Executive Officer and Chief Financial Officer, as appropriate to allow timely decisions regarding required disclosure.

41

Changes in Internal Control Over Financial Reporting

There were no changes in our internal control over financial reporting for the quarter ended March 31, 2013, that have materially affected, or are reasonably likely to materially affect, such control.

Limitations on Controls and Procedures

The effectiveness of our disclosure controls and procedures and our internal control over financial reporting is subject to various inherent limitations, including cost limitations, judgments used in decision making, assumptions about the likelihood of future events, the soundness of our systems, the possibility of human error, and the risk of fraud. Moreover, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions and the risk that the degree of compliance with policies or procedures may deteriorate over time. Because of these limitations, any system of disclosure controls and procedures or internal control over financial reporting may not be successful in preventing all errors or fraud or in making all material information known in a timely manner to the appropriate levels of management.

PART II.

OTHER INFORMATION

Item 1. Legal Proceedings

There have been no material changes in legal proceedings as described in our Annual Report on Form 10-K for the year ended December 31, 2012.

Item 1A. Risk Factors

There have been no material changes in risk factors described in our Annual Report on Form 10-K for the year ended December 31, 2012.

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds

(a) There were no unregistered sales of equity securities during the three months ended March 31, 2013.

(b) Not applicable.

(c) The following table provides information with respect to purchases made by or on behalf of us or any “affiliated purchasers” (as defined in Rule 10b-18(a)(3) under the Exchange Act), of our common stock during the three months ended Mach 31, 2013.

Period	Total Number of Shares Purchased (1)	Average Price Paid Per Share		Total Number of Shares Purchased as Part of Publicly Announced Plans or Programs	Maximum Number of Shares that May Yet Be Purchased Under the Plans or Programs
January 2013	—	$	—	—	Not Applicable
February 2013	25,677	17.43		—	Not Applicable
March 2013	—	—		—	Not Applicable
Total	25,677	$	15.23	—	Not Applicable

 (1) Represents shares purchased by the Company in satisfaction of minimum required income tax withholding requirements pursuant to the vesting of restricted stock.

Item 3. Defaults upon Senior Securities

None.

Item 4. Mine Safety Disclosures

Not applicable.

Item 5. Other Information

Not applicable or required.

42

Item 6.    Exhibits

3.1	Amended and Restated Articles of Incorporation dated March 5, 2010 (incorporated herein by reference to Exhibit 3.1 of the Company’s Current Report on Form 8-K/A filed on March 10, 2010)
3.2	Second Amended and Restated Bylaws dated January 27, 2011 (incorporated herein by reference to Exhibit 3.1 of the Company’s Current Report on Form 8-K/A filed on February 3, 2011)
4.1	Specimen of Series A preferred stock certificate of First Interstate BancSystem, Inc. (incorporated herein by reference to Exhibit 4.2 of the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2007)
10.1	Credit Agreement Re: Subordinated Term Note dated as of January 10, 2008, between First Interstate BancSystem, Inc. and First Midwest Bank (incorporated herein by reference to Exhibit 10.24 of the Company’s Current Report on Form 8-K filed on January 16, 2008)
10.2	Lease Agreement between Billings 401 Joint Venture and First Interstate Bank Montana dated September 20, 1985 and addendum thereto (incorporated herein by reference to Exhibit 10.4 of the Company’s Post-Effective Amendment No. 3 to Registration Statement on Form S-1, No. 033-84540, filed on September 29, 1994)
10.3†	First Interstate BancSystem’s Deferred Compensation Plan dated December 1, 2006 (incorporated herein by reference to Exhibit 10.9 of the Company’s Pre-Effective Amendment No. 3 to Registration Statement on Form S-1, No. 333-164380, filed on March 23, 2010)
10.4†	First Amendment to the First Interstate BancSystem’s Deferred Compensation Plan dated October 24, 2008 (incorporated herein by reference to Exhibit 10.10 of the Company’s Pre-Effective Amendment No. 3 to Registration Statement on Form S-1, No. 333-164380, filed on March 23, 2010)
10.5†	2001 Stock Option Plan (incorporated herein by reference to Exhibit 4.12 of the Company’s Registration Statement on Form S-8, No. 333-106495, filed on June 25, 2003)
10.6†	Second Amendment to 2001 Stock Option Plan (incorporated herein by reference to Exhibit 10.6 of the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2010)
10.7†	First Interstate BancSystem, Inc. 2006 Equity Compensation Plan (incorporated herein by reference to Appendix A of the Company’s 2006 Definitive Proxy Statement of Schedule 14A)
10.8†	Amendment to First Interstate BancSystem, Inc. 2006 Equity Compensation Plan (incorporated herein by reference to Exhibit 10.1 of the Company’s Current Report on Form 8-K filed on March 22, 2010)
10.9†	Second Amendment to First Interstate BancSystem, Inc. 2006 Equity Compensation Plan (incorporated herein by reference to Exhibit 10.9 of the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2010)
10.10*†	Third Amendment to the First Interstate BancSystem, Inc. 2006 Equity Compensation Plan
10.11†	Form of First Interstate BancSystem, Inc. 2006 Equity Compensation Plan Restricted Stock Agreement (Time) for Certain Executive Officers, (incorporated herein by reference to Exhibit 10.13 of the Company's Annual Report on form 10-K for the fiscal year ended December 31, 2008)
10.12†	Form of First Interstate BancSystem, Inc. 2006 Equity Compensation Plan Restricted Stock Agreement (Performance) for Certain Executive Officers, (incorporated herein by reference to Exhibit 10.1 of the Company's Current Report on form 8-K filed on February 13, 2013)
10.13	Trademark License Agreements between Wells Fargo & Company and First Interstate BancSystem, Inc. (incorporated herein by reference to Exhibit 10.11 of the Company’s Registration Statement on Form S-1, No. 333-25633 filed on April 22, 1997)
31.1*	Certification of Quarterly Report on Form 10-Q pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 by Chief Executive Officer
31.2*	Certification of Quarterly Report on Form 10-Q pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 by Chief Financial Officer
32*	Certification of Quarterly Report on Form 10-Q pursuant to Section 906 of the Sarbanes-Oxley Act of 2002
101**	Interactive data file

† Management contract or compensatory arrangement.

* Filed herewith.

** As provided in Rule 406T of Regulation S-T, this information is furnished and not filed for purposes of Sections 11 and 12 of the Securities Act of 1933 and Section 18 of the Securities Exchange Act of 1934.

43

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	FIRST INTERSTATE BANCSYSTEM, INC.
Date: April 30, 2013	/S/    ED GARDING
	Ed Garding
	President and Chief Executive Officer
Date: April 30, 2013	/S/    TERRILL R. MOORE
	Terrill R. Moore
	Executive Vice President and Chief Financial Officer

44

EX-10.10

Exhibit 10.10

Third Amendment

to the

First Interstate BancSystem, Inc.

2006 Equity Compensation Plan

This Third Amendment (the “Amendment') by First Interstate BancSystem, Inc., a Montana corporation (the “Company”), to its 2006 Equity Compensation Plan (the “2006 Plan”) was approved by the Board of Directors of the Company on March 29, 2013, and by the Company's shareholders on May 22, 2013.

WHEREAS, the Company previously adopted the 2006 Plan pursuant to which the Company may grant equity awards to its directors, officers and other employees in an effort to attract, retain and motivate individuals who are expected to make important contributions to the Company. The 2006 Plan was amended effective March 19, 2010 and September 23, 2010.

WHEREAS, the Compensation Committee of the Board of Directors of the Company (the “Board”) has recommended, and the Board has determined that it is in the best interests of the Company and its shareholders to amend the 2006 Plan in accordance with the provisions hereof.

NOW, THEREFORE, based on the foregoing recitals, the Company hereby agrees as follows:

1.Section 4.1 is revised to read in its entirety as follows:

4.1Reserved Stock. The number of shares of Common Stock to be reserved for purposes of granting Benefits under this Plan shall be 4,500,000.

2.Except as modified in this Third Amendment or as previously amended, all other terms of the 2006 Plan shall remain in full force and effect.

IN WITNESS WHEREOF, the undersigned has executed this Amendment effective as of the 22nd day of May, 2013.

COMPANY:

First Interstate BancSystem, Inc.

a Montana corporation

By: /s/ TERRILL R. MOORE

Terrill R. Moore

Executive Vice President &

Chief Financial Officer

EX-31.1

Exhibit 31.1

CERTIFICATION OF QUARTERLY REPORT ON FORM 10-Q

PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Ed Garding, certify that :

1. I have reviewed this quarterly report on Form 10-Q of First Interstate BancSystem, Inc;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a. designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes, as of the end of the period covered by this report based on such evaluation; and

c. evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of registrant’s board of directors (or persons performing the equivalent functions);

a. all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b. any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

DATE: April 30, 2013

/s/ ED GARDING

Ed Garding

President and Chief Executive Officer

EX-31.2

Exhibit 31.2

CERTIFICATION OF QUARTERLY REPORT ON FORM 10-Q

PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Terrill R. Moore, certify that :

1. I have reviewed this quarterly report on Form 10-Q of First Interstate BancSystem, Inc;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a. designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes, as of the end of the period covered by this report based on such evaluation; and

c. evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of registrant’s board of directors (or persons performing the equivalent functions);

a. all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b. any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

DATE: April 30, 2013

/s/ TERRILL R. MOORE

Terrill R. Moore

Executive Vice President and Chief Financial Officer

EX-32

Exhibit 32

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED

PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

The undersigned are the Chief Executive Officer and the Chief Financial Officer of First Interstate BancSystem, Inc. (the “Registrant”). This Certification is made pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. This Certification accompanies the Quarterly Report on Form 10-Q of the Registrant for the quarter ended March 31, 2013.

We certify that such Quarterly Report on Form 10-Q fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that the information contained in the Form 10-Q fairly presents, in all material respects, the financial condition and results of operations of the Registrant.

This Certification is executed as of April 30, 2013.

/s/ ED GARDING

Ed Garding

President and Chief Executive Officer

/s/ TERRILL R. MOORE

Terrill R. Moore

Executive Vice President and Chief Financial Officer

Chief Financial Officer

XML

Schedule of Loans Renegotiated in Troubled Debt Restructurings (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 notes		Dec. 31, 2012
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Loans Renegotiated in Troubled Debt Restructurings	$ 75,229		$ 76,597
Loans Renegotiated in Troubled Debt Restructurings, Non-Accrual Loans	39,442		44,665
Loans Renegotiated in Troubled Debt Restructurings, Accrual Loans	35,787		31,932
Number of Notes	15,000
Principle Balance at Restructure Date	6,617
Number of Notes	0
Balance	650
Interest only period
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	170
Extension of terms or maturity
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	567
Interest rate adjustment
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	5,610
Other
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	270	[1]
Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Number of Notes	11,000
Principle Balance at Restructure Date	6,037
Commercial real estate | Interest only period
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	120
Commercial real estate | Extension of terms or maturity
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	389
Commercial real estate | Interest rate adjustment
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	5,345
Commercial real estate | Other
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	183	[1]
Residential real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Number of Notes	0
Balance	278
Total real estate loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Number of Notes	11,000
Principle Balance at Restructure Date	6,037
Total real estate loans | Interest only period
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	120
Total real estate loans | Extension of terms or maturity
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	389
Total real estate loans | Interest rate adjustment
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	5,345
Total real estate loans | Other
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	183	[1]
Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Number of Notes	4,000
Principle Balance at Restructure Date	580
Number of Notes	1
Balance	372
Commercial | Interest only period
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	50
Commercial | Extension of terms or maturity
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	178
Commercial | Interest rate adjustment
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	265
Commercial | Other
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Principle Balance at Restructure Date	$ 87

[1]

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Supplemental Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Supplemental Cash Flow Information [Abstract]
Transferred Loans to OREO	$ 5,331	$ 13,978
Transferred Loans to Mortgage Servicing Assets	1,144	1,040
Transfer from Investments	$ 429

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Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Construction Contracts
Unrecorded Unconditional Purchase Obligation [Line Items]
Commitments to Purchase	$ 67
Held-to-maturity Securities | State, county and municipal securities
Unrecorded Unconditional Purchase Obligation [Line Items]
Commitments to Purchase	$ 960

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Investment Securities Realized Gains (Losses) on Investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 8	$ 31
Gross realized losses	$ 0	$ 0

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Loans (Tables)

3 Months Ended

Mar. 31, 2013

Receivables [Abstract]

Schedule of Loans by Class

The following table presents loans by class as of the dates indicated:

	March 31, 2013		December 31, 2012
Real estate loans:
Commercial	$	1,469,302	$	1,497,272
Construction:
Land acquisition & development	215,505		220,196
Residential	50,153		49,274
Commercial	65,228		65,059
Total construction loans	330,886		334,529
Residential	758,480		708,339
Agricultural	172,522		177,244
Total real estate loans	2,731,190		2,717,384
Consumer:
Indirect consumer	444,257		438,245
Other consumer	135,474		137,743
Credit card	56,633		60,806
Total consumer loans	636,364		636,794
Commercial	688,844		688,753
Agricultural	111,411		113,627
Other, including overdrafts	1,307		912
Loans held for investment	4,169,116		4,157,470
Mortgage loans held for sale	55,443		66,442
Total loans	$	4,224,559	$	4,223,912

Schedule of Recorded Investment in Past Due Loans by Class

The following tables present the contractual aging of the Company’s recorded investment in past due loans by class as of the period indicated:

							Total Loans
	30 - 59		60 - 89		> 90		30 or More
	Days		Days		Days		Days		Current		Non-accrual		Total
As of March 31, 2013	Past Due		Past Due		Past Due		Past Due		Loans		Loans		Loans
Real estate
Commercial	$	12,846	$	865	$	—	$	13,711	$	1,410,640	$	44,951	$	1,469,302
Construction:
Land acquisition & development	6,294		62		—		6,356		192,376		16,773		215,505
Residential	92		—		—		92		48,726		1,335		50,153
Commercial	2,173		—		—		2,173		56,572		6,483		65,228
Total construction loans	8,559		62		—		8,621		297,674		24,591		330,886
Residential	4,269		502		1,044		5,815		744,108		8,557		758,480
Agricultural	1,464		349		2		1,815		166,116		4,591		172,522
Total real estate loans	27,138		1,778		1,046		29,962		2,618,538		82,690		2,731,190
Consumer:
Indirect consumer	2,166		326		3		2,495		441,477		285		444,257
Other consumer	642		157		1		800		133,786		888		135,474
Credit card	308		222		467		997		55,614		22		56,633
Total consumer loans	3,116		705		471		4,292		630,877		1,195		636,364
Commercial	4,097		3,966		329		8,392		665,884		14,568		688,844
Agricultural	813		311		95		1,219		110,051		141		111,411
Other, including overdrafts			—		—		—		1,307		—		1,307
Loans held for investment	35,164		6,760		1,941		43,865		4,026,657		98,594		4,169,116
Mortgage loans originated for sale	—		—		—		—		55,443		—		55,443
Total loans	$	35,164	$	6,760	$	1,941	$	43,865	$	4,082,100	$	98,594	$	4,224,559

							Total Loans
	30 - 59		60 - 89		> 90		30 or More
	Days		Days		Days		Days		Current		Non-accrual		Total
As of December 31, 2012	Past Due		Past Due		Past Due		Past Due		Loans		Loans		Loans
Real estate
Commercial	$	5,449	$	3,163	$	2	$	8,614	$	1,438,142	$	50,516	$	1,497,272
Construction:
Land acquisition & development	3,371		2,121		318		5,810		195,077		19,309		220,196
Residential	283		—		—		283		46,816		2,175		49,274
Commercial	—		—		—		—		56,933		8,126		65,059
Total construction loans	3,654		2,121		318		6,093		298,826		29,610		334,529
Residential	3,896		969		1,085		5,950		691,963		10,426		708,339
Agricultural	1,187		—		218		1,405		171,009		4,830		177,244
Total real estate loans	14,186		6,253		1,623		22,062		2,599,940		95,382		2,717,384
Consumer:
Indirect consumer	3,218		512		32		3,762		434,200		283		438,245
Other consumer	1,044		104		31		1,179		135,574		990		137,743
Credit card	409		278		392		1,079		59,704		23		60,806
Total consumer loans	4,671		894		455		6,020		629,478		1,296		636,794
Commercial	5,463		1,064		216		6,743		671,414		10,596		688,753
Agricultural	1,710		361		—		2,071		111,031		525		113,627
Other, including overdrafts	—		—		—		—		912		—		912
Loans held for investment	26,030		8,572		2,294		36,896		4,012,775		107,799		4,157,470
Mortgage loans originated for sale	—		—		—		—		66,442		—		66,442
Total loans	$	26,030	$	8,572	$	2,294	$	36,896	$	4,079,217	$	107,799	$	4,223,912

Schedule of Recorded Investment in Impaired Loans

The following tables present information on the Company’s recorded investment in impaired loans as of dates indicated:

As of March 31, 2013	Unpaid Total Principal Balance		Recorded Investment With No Allowance		Recorded Investment With Allowance		Total Recorded Investment		Related Allowance
Real estate:
Commercial	$	82,456	$	34,042	$	38,695	$	72,737	$	4,429
Construction:
Land acquisition & development	25,929		13,976		6,560		20,536		1,703
Residential	1,925		1,335		—		1,335		—
Commercial	9,422		6,227		256		6,483		68
Total construction loans	37,276		21,538		6,816		28,354		1,771
Residential	11,649		6,181		2,595		8,776		1,132
Agricultural	5,415		1,724		3,098		4,822		1,035
Total real estate loans	136,796		63,485		51,204		114,689		8,367
Commercial	16,521		7,969		7,863		15,832		3,725
Agricultural	205		127		25		152		25
Total	$	153,522	$	71,581	$	59,092	$	130,673	$	12,117

As of December 31, 2012	Unpaid Total Principal Balance		Recorded Investment With No Allowance		Recorded Investment With Allowance		Total Recorded Investment		Related Allowance
Real estate:
Commercial	$	84,300	$	39,049	$	34,774	$	73,823	$	4,112
Construction:
Land acquisition & development	28,558		15,891		7,173		23,064		1,457
Residential	3,018		1,976		710		2,686		251
Commercial	10,447		7,785		340		8,125		69
Total construction loans	42,023		25,652		8,223		33,875		1,777
Residential	13,271		6,152		4,495		10,647		1,677
Agricultural	5,559		1,834		3,227		5,061		784
Total real estate loans	145,153		72,687		50,719		123,406		8,350
Commercial	12,770		9,036		3,206		12,242		1,919
Agricultural	589		509		28		537		28
Total	$	158,512	$	82,232	$	53,953	$	136,185	$	10,297

The following table presents the average recorded investment in and income recognized on impaired loans for the periods indicated:

	Three Months Ended March 31,
	2013				2012
	Average Recorded Investment		Income Recognized		Average Recorded Investment		Income Recognized
Real estate:
Commercial	$	73,936	$	338	$	88,657	$	188
Construction:
Land acquisition & development	22,641		441		62,227		3
Residential	2,259		—		9,208		18
Commercial	7,898		—		24,265		—
Total construction loans	32,798		441		95,700		21
Residential	10,519		4		18,072		160
Agricultural	4,948		4		7,268		56
Total real estate loans	122,201		787		209,697		425
Commercial	12,746		18		17,885		31
Agricultural	632		4		1,234		—
Total	$	135,579	$	809	$	228,816	$	456

Schedule of Loans Renegotiated in Troubled Debt Restructurings

The following table presents information on the Company's troubled debt restructurings during the previous 12 months for which there was a payment default during the periods indicated. The Company considers a payment default to occur on troubled debt restructurings when the loan is 90 days or more past due or was placed on non-accrual status after the modification.

	Three Months Ended March 31,
	Number of Notes	Balance
Residential real estate	1	$	278
Commercial	1	372
Total	2	$	650

The following table presents information on the Company's troubled debt restructurings that occurred during the three months ended March 31, 2013:    

	Number of Notes	Type of Concession								Principal Balance at Restructure Date
Three Months Ended March 31, 2013		Interest only period		Extension of terms or maturity		Interest rate adjustment		Other (1)
Real estate:
Commercial	11	$	120	$	389	$	5,345	$	183	$	6,037
Total real estate loans	11	120		389		5,345		183		6,037
Commercial	4	50		178		265		87		580
Total loans restructured during period	15	$	170	$	567	$	5,610	$	270	$	6,617

(1) Other includes concessions that reduce or defer payments for a specified period of time and/or do not fit into other designated categories.

Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator

The following tables present the Company’s recorded investment in criticized loans by class and credit quality indicator based on the most recent analysis performed as of the dates indicated:

As of March 31, 2013	Other Assets Especially Mentioned		Substandard		Doubtful		Total Criticized Loans
Real estate:
Commercial	$	89,207	$	127,083	$	16,110	$	232,400
Construction:
Land acquisition & development	29,171		22,977		4,231		56,379
Residential	2,132		1,728		801		4,661
Commercial	3,000		695		5,788		9,483
Total construction loans	34,303		25,400		10,820		70,523
Residential	9,890		11,185		2,981		24,056
Agricultural	19,062		6,705		3,097		28,864
Total real estate loans	152,462		170,373		33,008		355,843
Consumer:
Indirect consumer	704		1,660		79		2,443
Other consumer	587		1,120		436		2,143
Credit card	—		447		2,281		2,728
Total consumer loans	1,291		3,227		2,796		7,314
Commercial	41,399		22,072		7,996		71,467
Agricultural	2,493		1,423		25		3,941
Total	$	197,645	$	197,095	$	43,825	$	438,565

As of December 31, 2012	Other Assets Especially Mentioned		Substandard		Doubtful		Total Criticized Loans
Real estate:
Commercial	$	101,936	$	135,282	$	15,173	$	252,391
Construction:
Land acquisition & development	28,137		25,884		4,739		58,760
Residential	2,531		2,427		1,143		6,101
Commercial	3,000		795		7,383		11,178
Total construction loans	33,668		29,106		13,265		76,039
Residential	9,542		11,680		4,511		25,733
Agricultural	18,490		6,737		3,228		28,455
Total real estate loans	163,636		182,805		36,177		382,618
Consumer:
Indirect consumer	793		1,764		114		2,671
Other consumer	684		1,395		628		2,707
Credit card	—		415		2,085		2,500
Total consumer loans	1,477		3,574		2,827		7,878
Commercial	42,223		27,184		3,428		72,835
Agricultural	2,596		1,625		28		4,249
Total	$	209,932	$	215,188	$	42,460	$	467,580

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Schedule of Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Net accumulated other comprehensive income:
Net unrealized gain on investment securities available-for-sale	$ 14,065		$ 17,537
Net actuarial loss on defined benefit post-retirement benefit plans	(1,525)		(1,546)
Net accumulated other comprehensive income	$ 12,540	$ 15,991	$ 15,991

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OREO (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Real Estate Acquired Through Foreclosure [Roll Forward]
Beginning balance	$ 32,571		$ 37,452
Additions	5,331	13,978
Capitalized improvements	10	(331)
Valuation adjustments	(2,305)	(578)
Dispositions	(3,137)	(5,765)
Ending balance	$ 32,470	$ 44,756	$ 37,452

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Schedule of Recorded Investment in Past Due Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Loans held for investment	$ 4,169,116		$ 4,157,470
Mortgage loans held for sale	55,443		66,442
Total loans	4,224,559	4,158,616	4,223,912
Interest Income on Non-Accrual Loans if Accrued	1,352	2,702
Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	12,846		5,449
60 to 89 Days Past Due	865		3,163
Greater than 90 Days Past Due	0		2
Total Loans 30 or More Days Past Due	13,711		8,614
Current Loans	1,410,640		1,438,142
Non-accrual Loans	44,951		50,516
Loans held for investment	1,469,302		1,497,272
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	6,294		3,371
60 to 89 Days Past Due	62		2,121
Greater than 90 Days Past Due	0		318
Total Loans 30 or More Days Past Due	6,356		5,810
Current Loans	192,376		195,077
Non-accrual Loans	16,773		19,309
Loans held for investment	215,505		220,196
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	92		283
60 to 89 Days Past Due	0		0
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	92		283
Current Loans	48,726		46,816
Non-accrual Loans	1,335		2,175
Loans held for investment	50,153		49,274
Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	2,173		0
60 to 89 Days Past Due	0		0
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	2,173		0
Current Loans	56,572		56,933
Non-accrual Loans	6,483		8,126
Loans held for investment	65,228		65,059
Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	8,559		3,654
60 to 89 Days Past Due	62		2,121
Greater than 90 Days Past Due	0		318
Total Loans 30 or More Days Past Due	8,621		6,093
Current Loans	297,674		298,826
Non-accrual Loans	24,591		29,610
Loans held for investment	330,886		334,529
Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	4,269		3,896
60 to 89 Days Past Due	502		969
Greater than 90 Days Past Due	1,044		1,085
Total Loans 30 or More Days Past Due	5,815		5,950
Current Loans	744,108		691,963
Non-accrual Loans	8,557		10,426
Loans held for investment	758,480		708,339
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	1,464		1,187
60 to 89 Days Past Due	349		0
Greater than 90 Days Past Due	2		218
Total Loans 30 or More Days Past Due	1,815		1,405
Current Loans	166,116		171,009
Non-accrual Loans	4,591		4,830
Loans held for investment	172,522		177,244
Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	27,138		14,186
60 to 89 Days Past Due	1,778		6,253
Greater than 90 Days Past Due	1,046		1,623
Total Loans 30 or More Days Past Due	29,962		22,062
Current Loans	2,618,538		2,599,940
Non-accrual Loans	82,690		95,382
Loans held for investment	2,731,190		2,717,384
Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	2,166		3,218
60 to 89 Days Past Due	326		512
Greater than 90 Days Past Due	3		32
Total Loans 30 or More Days Past Due	2,495		3,762
Current Loans	441,477		434,200
Non-accrual Loans	285		283
Loans held for investment	444,257		438,245
Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	642		1,044
60 to 89 Days Past Due	157		104
Greater than 90 Days Past Due	1		31
Total Loans 30 or More Days Past Due	800		1,179
Current Loans	133,786		135,574
Non-accrual Loans	888		990
Loans held for investment	135,474		137,743
Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	308		409
60 to 89 Days Past Due	222		278
Greater than 90 Days Past Due	467		392
Total Loans 30 or More Days Past Due	997		1,079
Current Loans	55,614		59,704
Non-accrual Loans	22		23
Loans held for investment	56,633		60,806
Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	3,116		4,671
60 to 89 Days Past Due	705		894
Greater than 90 Days Past Due	471		455
Total Loans 30 or More Days Past Due	4,292		6,020
Current Loans	630,877		629,478
Non-accrual Loans	1,195		1,296
Loans held for investment	636,364		636,794
Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	4,097		5,463
60 to 89 Days Past Due	3,966		1,064
Greater than 90 Days Past Due	329		216
Total Loans 30 or More Days Past Due	8,392		6,743
Current Loans	665,884		671,414
Non-accrual Loans	14,568		10,596
Loans held for investment	688,844		688,753
Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	813		1,710
60 to 89 Days Past Due	311		361
Greater than 90 Days Past Due	95		0
Total Loans 30 or More Days Past Due	1,219		2,071
Current Loans	110,051		111,031
Non-accrual Loans	141		525
Loans held for investment	111,411		113,627
Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due			0
60 to 89 Days Past Due	0		0
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	0		0
Current Loans	1,307		912
Non-accrual Loans	0		0
Loans held for investment	1,307		912
Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	35,164		26,030
60 to 89 Days Past Due	6,760		8,572
Greater than 90 Days Past Due	1,941		2,294
Total Loans 30 or More Days Past Due	43,865		36,896
Current Loans	4,026,657		4,012,775
Non-accrual Loans	98,594		107,799
Loans held for investment	4,169,116		4,157,470
Mortgage loans originated for sale
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0		0
60 to 89 Days Past Due	0		0
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	0		0
Current Loans	55,443		66,442
Non-accrual Loans	0		0
Total loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	35,164		26,030
60 to 89 Days Past Due	6,760		8,572
Greater than 90 Days Past Due	1,941		2,294
Total Loans 30 or More Days Past Due	43,865		36,896
Current Loans	4,082,100		4,079,217
Non-accrual Loans	98,594		107,799
Total loans	$ 4,224,559		$ 4,223,912

XML

Schedule of Estimated Fair Values of Financial Instruments by Level of Valuation Inputs (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financial liabilities:
Preferred Stock, Pending Redemption	$ 0	$ 50,000
Carrying Amount
Financial assets:
Cash and cash equivalents	498,543	801,332
Investment securities available-for-sale	2,011,169	1,995,258
Investment securities held-to-maturity	210,426	208,223
Accrued interest receivable	29,375	28,869
Mortgage servicing rights	13,006	12,653
Net loans	4,126,655	4,123,401
Total financial assets	6,889,174	7,169,736
Financial liabilities:
Total deposits, excluding time deposits	4,684,664	4,854,927
Time deposits	1,343,681	1,385,484
Securities sold under repurchase agreements	467,205	505,785
Other borrowed funds	8	32
Accrued interest payable	6,433	6,502
Long-term debt	37,150	37,160
Preferred Stock, Pending Redemption		50,000
Subordinated debentures held by subsidiary trusts	82,477	82,477
Total financial liabilities	6,621,618	6,922,367
Estimated Fair Value
Financial assets:
Cash and cash equivalents	498,543	801,332
Investment securities available-for-sale	2,011,169	1,995,258
Investment securities held-to-maturity	220,115	218,933
Accrued interest receivable	29,375	28,869
Mortgage servicing rights	18,807	16,373
Net loans	4,139,777	4,142,426
Total financial assets	6,917,786	7,203,191
Financial liabilities:
Total deposits, excluding time deposits	4,684,664	4,854,927
Time deposits	1,351,742	1,394,403
Securities sold under repurchase agreements	467,205	505,785
Other borrowed funds	8	32
Accrued interest payable	6,433	6,502
Long-term debt	34,887	35,104
Preferred Stock, Pending Redemption		50,000
Subordinated debentures held by subsidiary trusts	66,080	62,409
Total financial liabilities	6,611,019	6,909,162
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	0	0
Investment securities available-for-sale	0	0
Investment securities held-to-maturity	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	0	0
Net loans	0	0
Total financial assets	0	0
Financial liabilities:
Total deposits, excluding time deposits	0	0
Time deposits	0	0
Securities sold under repurchase agreements	0	0
Other borrowed funds	0	0
Accrued interest payable	0	0
Long-term debt	0	0
Subordinated debentures held by subsidiary trusts	0	0
Total financial liabilities	0	0
Significant Other Observable Inputs (Level 2) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	498,543	801,332
Investment securities available-for-sale	2,011,169	1,995,258
Investment securities held-to-maturity	220,115	218,933
Accrued interest receivable	29,375	28,869
Mortgage servicing rights	18,807	16,373
Net loans	4,062,688	4,067,803
Total financial assets	6,840,697	7,128,568
Financial liabilities:
Total deposits, excluding time deposits	4,684,664	4,854,927
Time deposits	1,351,742	1,394,403
Securities sold under repurchase agreements	467,205	505,785
Other borrowed funds	8	32
Accrued interest payable	6,433	6,502
Long-term debt	34,887	35,104
Preferred Stock, Pending Redemption		50,000
Subordinated debentures held by subsidiary trusts	66,080	62,409
Total financial liabilities	6,611,019	6,909,162
Significant Unobservable Inputs (Level 3) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	0	0
Investment securities available-for-sale	0	0
Investment securities held-to-maturity	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	0	0
Net loans	77,089	74,623
Total financial assets	77,089	74,623
Financial liabilities:
Total deposits, excluding time deposits	0	0
Time deposits	0	0
Securities sold under repurchase agreements	0	0
Other borrowed funds	0	0
Accrued interest payable	0	0
Long-term debt	0	0
Subordinated debentures held by subsidiary trusts	0	0
Total financial liabilities	$ 0	$ 0

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Financial Instruments with Off-Balance Sheet Risk (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Entity Information [Line Items]
Credit Extension Commitments	$ 1,176,789
Credit Extension Commitments, Beyond One Year	304,030
Standby Letters of Credit
Entity Information [Line Items]
Credit Extension Commitments	71,407
Unused Credit Card Lines
Entity Information [Line Items]
Credit Extension Commitments	$ 362,247

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Basis of Presentation

3 Months Ended

Mar. 31, 2013

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Presentation

Basis of Presentation

In the opinion of management, the accompanying unaudited consolidated financial statements of First Interstate BancSystem, Inc. and subsidiaries (the “Company”) contain all adjustments (all of which are of a normal recurring nature) necessary to present fairly the financial position of the Company at March 31, 2013 and December 31, 2012, and the results of operations and cash flows for each of the three month periods ended March 31, 2013 and 2012, in conformity with U.S. generally accepted accounting principles. The balance sheet information at December 31, 2012 is derived from audited consolidated financial statements. Certain reclassifications, none of which were material, have been made to conform prior year financial statements to the March 31, 2013 presentation. These reclassifications did not change previously reported net income or stockholders’ equity.

These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2012. Operating results for the three months ended March 31, 2013 are not necessarily indicative of the results that may be expected for the year ending December 31, 2013.

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Capital Stock (Details) (USD $) In Thousands, unless otherwise specified					3 Months Ended
	Mar. 31, 2013 Class A Common Stock	Dec. 31, 2012 Class A Common Stock	Mar. 31, 2013 Class B Common Stock	Dec. 31, 2012 Class B Common Stock	Mar. 31, 2013 Series A Preferred Stock [Member]
Class of Stock [Line Items]
Common Stock, Shares, Outstanding	18,424,252	17,635,369	25,190,690	25,654,954
Preferred Stock, Aggregate Redemption Price					$ 50,150

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Regulatory Capital (Tables)

3 Months Ended

Mar. 31, 2013

Banking and Thrift [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations

Actual capital amounts and ratios and selected minimum regulatory thresholds for the Company and its bank subsidiary, First Interstate Bank (“FIB”), as of March 31, 2013 and December 31, 2012 are presented in the following tables:

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
March 31, 2013
Total risk-based capital:
Consolidated	$	766,478	15.9	%	$	385,443	8.0	%	NA		NA
FIB	707,053		14.7		383,593		8.0		$	479,491	10.0	%
Tier 1 risk-based capital:
Consolidated	677,787		14.1		192,721		4.0		NA		NA
FIB	634,648		13.2		191,796		4.0		$	287,695	6.0
Leverage capital ratio:
Consolidated	677,787		9.2		293,323		4.0		NA		NA
FIB	634,648		8.7		292,739		4.0		$	365,924	5.0

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
December 31, 2012
Total risk-based capital:
Consolidated	$	748,431	15.6	%	$	384,014	8.0	%	NA		NA
FIB	697,695		14.6		382,245		8.0		$	477,806	10.0	%
Tier 1 risk-based capital:
Consolidated	652,929		13.6		192,007		4.0		NA		NA
FIB	622,466		13.0		191,122		4.0		$	286,683	6.0
Leverage capital ratio:
Consolidated	652,929		8.8		296,559		4.0		NA		NA
FIB	622,466		8.4		296,061		4.0		$	370,077	5.0

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Earnings per Share (Tables)

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Computation of Basic and Diluted Earnings per Share

The following table sets forth the computation of basic and diluted earnings per share for the three month periods ended March 31, 2013 and 2012.

	Three Months Ended March 31,
	2013		2012
Net income	$	20,044	$	12,214
Less preferred stock dividends	—		853
Net income available to common shareholders, basic and diluted	$	20,044	$	11,361
Weighted average common shares outstanding for basic earnings per share computation	43,140,409		42,873,769
Dilutive effects of stock-based compensation	287,973		108,774
Weighted average common shares outstanding for diluted earnings per common share computation	43,428,382		42,982,543
Basic earnings per common share	$	0.46	$	0.26
Diluted earnings per common share	$	0.46	$	0.26

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Computation of Basic and Diluted Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net Income (Loss) Available to Common Stockholders, Basic
Net income	$ 20,044	$ 12,214
Preferred stock dividends	0	853
Net income available to common stockholders	$ 20,044	$ 11,361
Weighted Average Number of Shares Outstanding, Basic and Diluted
Weighted average common shares outstanding for basic earnings per share computation	43,140,409	42,873,769
Dilutive effect of stock-based compensation	287,973	108,774
Weighted average common shares outstanding for diluted earnings per common share computation	43,428,382	42,982,543
Earnings Per Share, Basic and Diluted
Basic earnings per common share	$ 0.46	$ 0.26
Diluted earnings per common share	$ 0.46	$ 0.26
Stock Options
Earnings Per Share, Basic and Diluted [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,025,419	2,657,668
Unvested Restricted Stock
Earnings Per Share, Basic and Diluted [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	61,760	48,196

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Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2013

Equity [Abstract]

Schedule of Comprehensive Income (Loss)

The gross amounts of each component of other comprehensive income and the related tax effects are as follows:

	Pre-tax						Tax Expense (Benefit)						Net of Tax
Three Months Ended March 31,	2013			2012			2013			2012			2013			2012
Investment securities available-for sale:
Change in net unrealized gain during period	$	(5,717	)	$	755		$	(2,250	)	$	296		$	(3,467	)	$	459
Reclassification adjustment for net gains included in net income	(8		)	(31		)	(3		)	(12		)	(5		)	(19		)
Defined benefits post-retirement benefit plan:
Change in net actuarial loss	35			33			14			13			21			20
Total other comprehensive income	$	(5,690	)	$	757		$	(2,239	)	$	297		$	(3,451	)	$	460

Schedule of Accumulated Other Comprehensive Income (Loss)

The components of accumulated other comprehensive income, net of income taxes, are as follows:

	March 31, 2013			December 31, 2012
Net unrealized gain on investment securities available-for-sale	$	14,065		$	17,537
Net actuarial loss on defined benefit post-retirement benefit plans	(1,525		)	(1,546		)
Net accumulated other comprehensive income	$	12,540		$	15,991

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Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring Basis

Financial assets and financial liabilities measured at fair value on a recurring basis are as follows:

			Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale:
Obligations of U.S. government agencies	$	779,922	$	—	$	779,922	$	—
U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,230,738		—		1,230,738		—
Private mortgage-backed securities	509		—		509		—
Mortgage servicing rights	18,807		—		18,807		—

			Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale:
Obligations of U.S. government agencies	$	754,856	$	—	$	754,856	$	—
U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,239,851		—		1,239,851		—
Private mortgage-backed securities	551		—		551		—
Mortgage servicing rights	16,373		—		16,373		—

Schedule of Financial Assets and Financial Liabilities Measured at Fair Value on a Non-Recurring Basis

The following table presents information about the Company’s assets and liabilities measured at fair value on a non-recurring basis.

			Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Impaired loans	$	77,089	$	—	$	—	$	77,089
Other real estate owned	14,372		—		—		14,372
Long-lived assets to be disposed of by sale	496		—		—		496
			Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Impaired loans	$	74,623	$	—	$	—	$	74,623
Other real estate owned	15,745		—		—		15,745
Long-lived assets to be disposed of by sale	496		—		—		496

Schedule of Estimated Fair Values of Financial Instruments by Level of Valuation Inputs

The estimated fair values of financial instruments that are reported at amortized cost in the Company's consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, are as follows:

					Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Carrying Amount		Estimated Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	$	498,543	$	498,543	$	—	$	498,543	$	—
Investment securities available-for-sale	2,011,169		2,011,169		—		2,011,169		—
Investment securities held-to-maturity	210,426		220,115		—		220,115		—
Accrued interest receivable	29,375		29,375		—		29,375		—
Mortgage servicing rights, net	13,006		18,807		—		18,807		—
Net loans	4,126,655		4,139,777		—		4,062,688		77,089
Total financial assets	$	6,889,174	$	6,917,786	$	—	$	6,840,697	$	77,089
Financial liabilities:
Total deposits, excluding time deposits	$	4,684,664	$	4,684,664	$	—	$	4,684,664	$	—
Time deposits	1,343,681		1,351,742		—		1,351,742		—
Securities sold under repurchase agreements	467,205		467,205		—		467,205		—
Other borrowed funds	8		8		—		8		—
Accrued interest payable	6,433		6,433		—		6,433		—
Long-term debt	37,150		34,887		—		34,887		—
Subordinated debentures held by subsidiary    trusts	82,477		66,080		—		66,080		—
Total financial liabilities	$	6,621,618	$	6,611,019	$	—	$	6,611,019	$	—

					Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Carrying Amount		Estimated Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	$	801,332	$	801,332	$	—	$	801,332	$	—
Investment securities available-for-sale	1,995,258		1,995,258		—		1,995,258		—
Investment securities held-to-maturity	208,223		218,933		—		218,933		—
Accrued interest receivable	28,869		28,869		—		28,869		—
Mortgage servicing rights, net	12,653		16,373		—		16,373		—
Net loans	4,123,401		4,142,426		—		4,067,803		74,623
Total financial assets	$	7,169,736	$	7,203,191	$	—	$	7,128,568	$	74,623
Financial liabilities:
Total deposits, excluding time deposits	$	4,854,927	$	4,854,927	$	—	$	4,854,927	$	—
Time deposits	1,385,484		1,394,403		—		1,394,403		—
Securities sold under repurchase agreements	505,785		505,785		—		505,785		—
Other borrowed funds	32		32		—		32		—
Accrued interest payable	6,502		6,502		—		6,502		—
Long-term debt	37,160		35,104		—		35,104		—
Preferred stock pending redemption	50,000		50,000				50,000
Subordinated debentures held by subsidiary    trusts	82,477		62,409		—		62,409		—
Total financial liabilities	$	6,922,367	$	6,909,162	$	—	$	6,909,162	$	—

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Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 20,044	$ 12,214
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	500	11,250
Net (gain) loss on disposal of property and equipment	(20)	42
Depreciation and amortization	4,203	4,302
Net premium amortization on investment securities	4,082	2,678
Net gains on investment securities transactions	(8)	(31)
Net gains on sales of mortgage loans held for sale	(7,898)	(5,927)
Net gain on sale of OREO	(820)	74
OREO valuation adjustments	2,305	578
Net impairment (reversal of impairment) of mortgage servicing rights	(48)	(868)
Gain Loss on Sale of Mortgage Servicing	0	19
Deferred income tax expense	1,853	(282)
Net increase in cash surrender value of company-owned life insurance policies	(429)	(462)
Stock-based compensation expense	695	643
Tax benefits from stock-based compensation expense	202	114
Excess tax benefits from stock-based compensation	(165)	(94)
Originations of mortgage loans held for sale, net of sales	17,753	(272)
Changes in operating assets and liabilities:
Increase in interest receivable	(506)	1,567
Decrease in other assets	(64)	907
Decrease in accrued interest payable	(69)	132
Decrease in accounts payable and accrued expenses	(1,861)	1,744
Net cash provided by operating activities	39,749	28,290
Cash flows from investing activities:
Purchases of held-to-maturity investment securities	(6,347)	(7,592)
Purchases of available-for-sale investment securities	(227,040)	(222,413)
Proceeds from maturities and paydowns of held-to-maturity investment securities	3,512	2,193
Proceeds from maturities and paydowns of available-for-sale investment securities	201,621	282,083
Proceeds from sales of mortgage servicing rights	311	907
Extensions of credit to customers, net of repayments	(22,997)	10,027
Recoveries of loans charged-off	2,913	1,158
Proceeds from sales of OREO	3,957	5,691
Capital contribution to unconsolidated equity method investee	(650)	(3,453)
Net cash used in investing activities	(44,720)	68,601
Cash flows from financing activities:
Net increase (decrease) in deposits	(212,066)	83,863
Net decrease in repurchase agreements	(38,580)	(25,185)
Net increase (decrease) in short-term borrowings	(24)	(1)
Repayments of long-term debt	(10)	(9)
Redemption of preferred stock	(50,000)	0
Proceeds from issuance of common stock	3,145	1,068
Excess tax benefits from stock-based compensation	165	94
Purchase and retirement of common stock	(448)	(256)
Dividends paid to common stockholders	0	(5,135)
Dividends paid to preferred stockholders	0	(853)
Net cash provided by (used in) financing activities	(297,818)	53,586
Net increase (decrease) in cash and cash equivalents	(302,789)	150,477
Cash and cash equivalents at beginning of period	801,332	472,447
Cash and cash equivalents at end of period	498,543	622,924
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	3,376	100
Cash paid during the period for interest expense	$ 5,859	$ 8,291

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Amortized Cost and Approximate Fair Values of Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Schedule of Available for Sale and Held-to-Maturity Securities [Line Items]
Available-for-Sale Securities, Gross Realized Gains	$ 8	$ 31
Available-for-sale Securities, Gross Realized Losses	0	0
Available-for-Sale:
Available-for-Sale, Amortized Cost	1,987,964		1,966,417
Available-for-Sale, Gross Unrealized Gains	27,049		30,531
Available-for-Sale, Gross Unrealized Losses	(3,844)		(1,690)
Available-for-Sale, Estimated Fair Value	2,011,169		1,995,258
Held-to-Maturity:
Held-to-Maturity, Amortized Cost	210,426		208,223
Held-to-Maturity, Gross Unrealized Gains	9,977		10,899
Held-to-Maturity, Gross Unrealized Losses	(288)		(189)
Held-to-Maturity, Estimated Fair Value	220,115		218,933
Obligations of U.S. government agencies
Available-for-Sale:
Available-for-Sale, Amortized Cost	777,044		751,501
Available-for-Sale, Gross Unrealized Gains	3,220		3,518
Available-for-Sale, Gross Unrealized Losses	(342)		(163)
Available-for-Sale, Estimated Fair Value	779,922		754,856
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations
Available-for-Sale:
Available-for-Sale, Amortized Cost	1,210,425		1,214,377
Available-for-Sale, Gross Unrealized Gains	23,814		27,000
Available-for-Sale, Gross Unrealized Losses	(3,501)		(1,526)
Available-for-Sale, Estimated Fair Value	1,230,738		1,239,851
Private mortgage-backed securities
Available-for-Sale:
Available-for-Sale, Amortized Cost	495		539
Available-for-Sale, Gross Unrealized Gains	15		13
Available-for-Sale, Gross Unrealized Losses	(1)		(1)
Available-for-Sale, Estimated Fair Value	509		551
State, county and municipal securities
Held-to-Maturity:
Held-to-Maturity, Amortized Cost	192,241		192,875
Held-to-Maturity, Gross Unrealized Gains	9,881		10,835
Held-to-Maturity, Gross Unrealized Losses	(282)		(176)
Held-to-Maturity, Estimated Fair Value	201,840		203,534
Corporate securities
Held-to-Maturity:
Held-to-Maturity, Amortized Cost	18,185		14,975
Held-to-Maturity, Gross Unrealized Gains	96		64
Held-to-Maturity, Gross Unrealized Losses	(6)		(13)
Held-to-Maturity, Estimated Fair Value	18,275		15,026
Other securities
Held-to-Maturity:
Held-to-Maturity, Amortized Cost			373
Held-to-Maturity, Gross Unrealized Gains			0
Held-to-Maturity, Gross Unrealized Losses			0
Held-to-Maturity, Estimated Fair Value			$ 373

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Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	$ 4,169,116	$ 4,157,470
Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,469,302	1,497,272
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	215,505	220,196
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	50,153	49,274
Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	65,228	65,059
Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	330,886	334,529
Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	758,480	708,339
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	172,522	177,244
Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,731,190	2,717,384
Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	444,257	438,245
Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	135,474	137,743
Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	56,633	60,806
Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	636,364	636,794
Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	688,844	688,753
Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	111,411	113,627
Other Assets Especially Mentioned
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	197,645	209,932
Other Assets Especially Mentioned | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	89,207	101,936
Other Assets Especially Mentioned | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	29,171	28,137
Other Assets Especially Mentioned | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,132	2,531
Other Assets Especially Mentioned | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	3,000	3,000
Other Assets Especially Mentioned | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	34,303	33,668
Other Assets Especially Mentioned | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	9,890	9,542
Other Assets Especially Mentioned | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	19,062	18,490
Other Assets Especially Mentioned | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	152,462	163,636
Other Assets Especially Mentioned | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	704	793
Other Assets Especially Mentioned | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	587	684
Other Assets Especially Mentioned | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	0	0
Other Assets Especially Mentioned | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,291	1,477
Other Assets Especially Mentioned | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	41,399	42,223
Other Assets Especially Mentioned | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,493	2,596
Substandard
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	197,095	215,188
Substandard | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	127,083	135,282
Substandard | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	22,977	25,884
Substandard | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,728	2,427
Substandard | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	695	795
Substandard | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	25,400	29,106
Substandard | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	11,185	11,680
Substandard | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	6,705	6,737
Substandard | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	170,373	182,805
Substandard | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,660	1,764
Substandard | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,120	1,395
Substandard | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	447	415
Substandard | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	3,227	3,574
Substandard | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	22,072	27,184
Substandard | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,423	1,625
Doubtful
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	43,825	42,460
Doubtful | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	16,110	15,173
Doubtful | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	4,231	4,739
Doubtful | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	801	1,143
Doubtful | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	5,788	7,383
Doubtful | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	10,820	13,265
Doubtful | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,981	4,511
Doubtful | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	3,097	3,228
Doubtful | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	33,008	36,177
Doubtful | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	79	114
Doubtful | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	436	628
Doubtful | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,281	2,085
Doubtful | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,796	2,827
Doubtful | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	7,996	3,428
Doubtful | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	25	28
Total Criticized Loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	438,565	467,580
Total Criticized Loans | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	232,400	252,391
Total Criticized Loans | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	56,379	58,760
Total Criticized Loans | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	4,661	6,101
Total Criticized Loans | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	9,483	11,178
Total Criticized Loans | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	70,523	76,039
Total Criticized Loans | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	24,056	25,733
Total Criticized Loans | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	28,864	28,455
Total Criticized Loans | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	355,843	382,618
Total Criticized Loans | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,443	2,671
Total Criticized Loans | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,143	2,707
Total Criticized Loans | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,728	2,500
Total Criticized Loans | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	7,314	7,878
Total Criticized Loans | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	71,467	72,835
Total Criticized Loans | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	$ 3,941	$ 4,249

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Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets
Cash and due from banks	$ 116,399	$ 177,978
Federal funds sold	4,856	730
Interest bearing deposits in banks	377,288	622,624
Total cash and cash equivalents	498,543	801,332
Investment securities:
Available-for-sale	2,011,169	1,995,258
Held-to-maturity (estimated fair values of $199,078 and $161,877 at September 30, 2012 and December 31, 2011, respectively)	210,426	208,223
Total investment securities	2,221,595	2,203,481
Loans held for investment	4,169,116	4,157,470
Mortgage loans held for sale	55,443	66,442
Total loans	4,224,559	4,223,912
Less allowance for loan losses	97,904	100,511
Net loans	4,126,655	4,123,401
Premises and equipment, net of accumulated depreciation	185,237	187,565
Goodwill	183,673	183,673
Company-owned life insurance	77,158	76,729
Other real estate owned (OREO)	32,470	32,571
Accrued interest receivable	29,375	28,869
Mortgage servicing rights, net of accumulated amortization and impairment reserve	13,006	12,653
Deferred tax asset, net	2,965	2,597
Core deposit intangibles, net of accumulated amortization	5,582	5,937
Other assets	63,058	62,953
Total assets	7,439,317	7,721,761
Deposits:
Non-interest bearing	1,406,892	1,495,309
Interest bearing	4,621,453	4,745,102
Total deposits	6,028,345	6,240,411
Securities sold under repurchase agreements	467,205	505,785
Accounts payable and accrued expenses	46,326	48,208
Accrued interest payable	6,433	6,502
Long-term debt	37,150	37,160
Other borrowed funds	8	32
Preferred stock pending redemption	0	50,000
Subordinated debentures held by subsidiary trusts	82,477	82,477
Total liabilities	6,667,944	6,970,575
Stockholders' equity:
Nonvoting noncumulative preferred stock without par value; authorized 100,000 shares; issued and outstanding 5,000 shares as of March 31, 2012 and December 31, 2011	0	0
Common stock	274,929	271,335
Retained earnings	483,904	463,860
Accumulated other comprehensive income, net	12,540	15,991
Total stockholders' equity	771,373	751,186
Total liabilities and stockholders' equity	$ 7,439,317	$ 7,721,761

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Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Total risk-based capital:
Actual Amount	$ 766,478	$ 748,431
Actual Ratio	15.90%	15.60%
Adequately Capitalized Amount	385,443	384,014
Adequately Capitalized Ratio	8.00%	8.00%
Tier 1 risk-based capital:
Actual Amount	677,787	652,929
Actual Ratio	14.10%	13.60%
Adequately Capitalized Amount	192,721	192,007
Adequately Capitalized Ratio	4.00%	4.00%
Leverage capital ratio:
Actual Ratio	9.20%	8.80%
Adequately Capitalized Amount	293,323	296,559
Adequately Capitalized Ratio	4.00%	4.00%
FIB
Total risk-based capital:
Actual Amount	707,053	697,695
Actual Ratio	14.70%	14.60%
Adequately Capitalized Amount	383,593	382,245
Adequately Capitalized Ratio	8.00%	8.00%
Well Capitalized Amount	479,491	477,806
Well Capitalized Ratio	10.00%	10.00%
Tier 1 risk-based capital:
Actual Amount	634,648	622,466
Actual Ratio	13.20%	13.00%
Adequately Capitalized Amount	191,796	191,122
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	287,695	286,683
Well Capitalized Ratio	6.00%	6.00%
Leverage capital ratio:
Actual Ratio	8.70%	8.40%
Adequately Capitalized Amount	292,739	296,061
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	$ 365,924	$ 370,077
Well Capitalized Ratio	5.00%	5.00%

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Consolidated Statements of Changes in Stockholders Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Preferred stock	Common stock	Retained earnings	Accumulated other comprehensive income
Beginning Balance at Dec. 31, 2011	$ 771,020	$ 50,000	$ 266,842	$ 435,144	$ 19,034
Comprehensive income:
Net income	12,214	0	0	12,214	0
Other comprehensive income, net of tax	460	0	0	0	460
Common stock transactions:
Common shares purchased and retired 25,677 and 17,904 in 2013 and 2012 respectively	(256)	0	(256)	0	0
Common shares issued 2,358 in 2012	0	0	0	0	0
Non-vested common shares issued 108,873 and 122,912 in 2013 and 2012 respectively	0	0	0	0	0
1,815 and 1,556 non-vested common shares forfeited in 2013 and 2012 respectively	0	0	0	0	0
243,238 and 100,991 stock options exercised, net of 87,933 and 37,397 shares tendered in payment of option price and income tax withholding amounts in 2013 and 2012 respectively	1,068	0	1,068	0	0
Tax benefit of stock-based compensation	114	0	114	0	0
Stock-based compensation expense	643	0	643	0	0
Cash dividends declared:
Common ($0.12) per share in 2012	(5,135)	0	0	(5,135)	0
Preferred (6.75%) per share in 2012	(853)	0	0	(853)	0
Ending Balance at Mar. 31, 2012	779,275	50,000	268,411	441,370	19,494
Beginning Balance at Dec. 31, 2012	751,186	0	271,335	463,860	15,991
Comprehensive income:
Net income	20,044	0	0	20,044	0
Other comprehensive income, net of tax	(3,451)	0	0	0	(3,451)
Common stock transactions:
Common shares purchased and retired 25,677 and 17,904 in 2013 and 2012 respectively	(448)	0	(448)	0	0
Non-vested common shares issued 108,873 and 122,912 in 2013 and 2012 respectively	0	0	0	0	0
1,815 and 1,556 non-vested common shares forfeited in 2013 and 2012 respectively	0	0	0	0	0
243,238 and 100,991 stock options exercised, net of 87,933 and 37,397 shares tendered in payment of option price and income tax withholding amounts in 2013 and 2012 respectively	3,145	0	3,145	0	0
Tax benefit of stock-based compensation	202	0	202	0	0
Stock-based compensation expense	695	0	695	0	0
Ending Balance at Mar. 31, 2013	$ 771,373	$ 0	$ 274,929	$ 483,904	$ 12,540

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Maturities of Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Rolling Maturity
Available-for-Sale Amortized Cost, Within One Year	$ 400,147
Available-for-Sale Amortized Cost, After One Year but Within Five Years	1,127,952
Available-for-Sale Amortized Cost, After Five Years but Within Ten Years	375,101
Available-for-Sale Amortized Cost, After Ten Years	84,764
Available-for-Sale Amortized Cost, Total	1,987,964
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity
Available-for-Sale Estimated Fair Value, Within One Year	405,641
Available-for-Sale Estimated Fair Value, After One Year but Within Five Years	1,141,233
Available-for-Sale Estimated Fair Value, After Ten Years	378,108
Available-for-Sale Estimated Fair Value, After Five Years but Within Ten Years	86,187
Available-for-Sale, Estimated Fair Value	2,011,169	1,995,258
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount
Held-to-Maturity Amortized Cost, Within One Year	3,877
Held-to-Maturity Amortized Cost, After One Year but Within Five Years	52,321
Held-to-Maturity Amortized Cost, After Five Years but Within Ten Years	86,803
Held-to-Maturity Amortized Cost, After Ten Years	67,425
Held-to-Maturity Amortized Cost, Total	210,426
Held-to-maturity Securities, Debt Maturities, Fair Value, Rolling Maturity
Held-to-Maturity Estimated Fair Value, Within One Year	3,925
Held-to-Maturity Estimated Fair Value, After One Year but Within Five Years	53,266
Held-to-Maturity Estimated Fair Value, After Five Years but Within Ten Years	90,886
Held-to-Maturity Estimated Fair Value, After Ten Years	72,038
Held-to-Maturity Estimated Fair Value, Total	220,115
Callable Within One Year
Available-for-sale Securities and Held-to-maturity Securities
Investment Securities Primarily Classified as Available-for-Sale, Amortized Costs, After One Year but Within Five Years	438,562
Investment Securities Primarily Classified as Available-for-Sale, Fair Value, After One Year but Within Five Years	438,990
Callable Structured Notes
Available-for-sale Securities and Held-to-maturity Securities
Investment Securities Primarily Classified as Available-for-Sale, Amortized Costs, After One Year but Within Five Years	130,375
Investment Securities Primarily Classified as Available-for-Sale, Fair Value, After One Year but Within Five Years	$ 130,572

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Recent Authoritative Accounting Guidance

3 Months Ended

Mar. 31, 2013

Accounting Changes and Error Corrections [Abstract]

Recent Authoritative Accounting Guidance

Recent Authoritative Accounting Guidance

ASU 2011-11, “Balance Sheet (Topic 210) - Disclosures about Offsetting Assets and Liabilities.” ASU 2011-11 amends Topic 210-Balance Sheet to require an entity to disclose both gross and net information about financial instruments that are eligible for offset in the statement of financial position and/or subject to a master netting arrangement or similar agreement. In January 2013, the Financial Accounting Standards Board, or FASB, issued ASU 2013-01, "Clarifying the Scope and Disclosures about Offsetting Assets and Liabilities," to clarify that the scope of ASU 2011-11 applies to derivatives accounted for in accordance with Topic 815, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset or subject to an enforceable master netting arrangement or similar agreement. ASU 2013-01 also clarifies that other types of financial assets and financial liabilities subject to a master netting arrangement or similar agreement are not subject to the provisions of ASU 2011-11. ASU 2011-11 and ASU 2013-01 became effective for the Company on January 1, 2013, and did not have a significant impact on the Company's consolidated financial statements, results of operations or liquidity.

ASU 2013-02 “Comprehensive Income (Topic 220) - Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income.” ASU 2013-02 requires entities to provide information about amounts reclassified out of accumulated other comprehensive income by component. The amendments in ASU 2013-02 require entities to present, either on the face of the income statement or in the notes significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income but only if the amount reclassified is required by U.S. GAAP to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income, entities are required to cross-reference to other disclosures required under U.S. GAAP that provide additional detail about those amounts. ASU 2013-02 became effective for the Company on January 1, 2013, and did not have a significant impact on the Company's consolidated financial statements, results of operations or liquidity.

ASU 2013-04 "Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date." ASU 2013-04 requires an entity to measure obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of (a) the amount the reporting entity agreed to pay on the basis of its arrangement among its co-obligors and (b) any additional amount the reporting entity expects to pay on behalf of its co-obligors. The amendments in ASU 2013-04 also requires an entity to disclose the nature, amount and other information about those obligations. ASU 2013-04 is effective for fiscal years, and interim period within those years, beginning after December 15, 2013, and is applied retrospectively to all prior periods presented. The Company does not expect amendments in ASU 2013-04 to impact the Company's consolidated financial statements, results of operations or liquidity.

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Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 4,169,116	$ 4,157,470
Mortgage loans held for sale	55,443	66,442
Total loans	4,224,559	4,223,912	4,158,616
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,469,302	1,497,272
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	215,505	220,196
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	50,153	49,274
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	65,228	65,059
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	330,886	334,529
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	758,480	708,339
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	172,522	177,244
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	2,731,190	2,717,384
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	444,257	438,245
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	135,474	137,743
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	56,633	60,806
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	636,364	636,794
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	688,844	688,753
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	111,411	113,627
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 1,307	$ 912

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Investment Securities (Tables)

3 Months Ended

Mar. 31, 2013

Investments, Debt and Equity Securities [Abstract]

Amortized Cost and Approximate Fair Values of Investment Securities

The amortized cost and approximate fair values of investment securities are summarized as follows:

March 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-Sale:
Obligations of U.S. government agencies	$	777,044	$	3,220	$	(342	)	$	779,922
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,210,425		23,814		(3,501		)	1,230,738
Private mortgage-backed securities	495		15		(1		)	509
Total	$	1,987,964	$	27,049	$	(3,844	)	$	2,011,169

March 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Held-to Maturity:
State, county and municipal securities	$	192,241	$	9,881	$	(282	)	$	201,840
Corporate securities	18,185		96		(6		)	18,275
Total	$	210,426	$	9,977	$	(288	)	$	220,115

December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-Sale:
Obligations of U.S. government agencies	$	751,501	$	3,518	$	(163	)	$	754,856
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,214,377		27,000		(1,526		)	1,239,851
Private mortgage-backed securities	539		13		(1		)	551
Total	$	1,966,417	$	30,531	$	(1,690	)	$	1,995,258

December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Held-to Maturity:
State, county and municipal securities	$	192,875	$	10,835	$	(176	)	$	203,534
Corporate securities	14,975		64		(13		)	15,026
Other securities	373		—		—			373
Total	$	208,223	$	10,899	$	(189	)	$	218,933

Realized Gains (Losses) on Investments

Gross realized gains and losses from the disposition of investment securities are summarized in the following table:

	Three Months Ended March 31,
	2013		2012
Gross realized gains	$	8	$	31
Gross realized losses	—		—

Gross Unrealized Losses and Fair Values of Investment Securities

The following tables show the gross unrealized losses and fair values of investment securities, aggregated by investment category, and the length of time individual investment securities have been in a continuous unrealized loss position, as of March 31, 2013 and December 31, 2012

	Less than 12 Months					12 Months or More					Total
March 31, 2013	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale:
Obligations of U.S. government agencies	$	182,957	$	(342	)	$	—	$	—		$	182,957	$	(342	)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	365,181		(3,501		)	—		—			365,181		(3,501		)
Private mortgage-backed securities	—		—			125		(1		)	125		(1		)
Total	$	548,138	$	(3,843	)	$	125	$	(1	)	$	548,263	$	(3,844	)

	Less than 12 Months					12 Months or More					Total
March 31, 2013	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Held-to-Maturity:
State, county and municipal securities	$	24,188	$	(276	)	$	525	$	(6	)	$	24,713	$	(282	)
Corporate securities	3,239		(6		)	—		—			3,239		(6		)
Total	$	27,427	$	(282	)	$	525	$	(6	)	$	27,952	$	(288	)

	Less than 12 Months					12 Months or More					Total
December 31, 2012	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale:
Obligations of U.S. government agencies	$	93,982	$	(163	)	$	—	$	—		$	93,982	$	(163	)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	250,198		(1,526		)	—		—			250,198		(1,526		)
Private mortgage-backed securities	—		—			137		(1		)	137		(1		)
Total	$	344,180	$	(1,689	)	$	137	$	(1	)	$	344,317	$	(1,690	)

	Less than 12 Months					12 Months or More					Total
December 31, 2012	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Held-to-Maturity:
State, county and municipal securities	$	19,389	$	(168	)	$	557	$	(8	)	$	19,946	$	(176	)
Corporate securities	9,312		(13		)	—		—			9,312		(13		)
Total	$	28,701	$	(181	)	$	557	$	(8	)	$	29,258	$	(189	)

Maturities of Investment Securities

Maturities of investment securities at March 31, 2013 are shown below. Maturities of mortgage-backed securities have been adjusted to reflect shorter maturities based upon estimated prepayments of principal. All other investment securities maturities are shown at contractual maturity dates.

	Available-for-Sale				Held-to-Maturity
March 31, 2013	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Within one year	$	400,147	$	405,641	$	3,877	$	3,925
After one year but within five years	1,127,952		1,141,233		52,321		53,266
After five years but within ten years	375,101		378,108		86,803		90,886
After ten years	84,764		86,187		67,425		72,038
Total	$	1,987,964	$	2,011,169	$	210,426	$	220,115

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Consolidated Statements of Changes in Stockholders Equity (Unaudited) (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Common stock
Common stock transactions:
Common shares purchased and retired	25,677	17,904
Common shares issued	0	2,358
Non-vested common shares issued	108,873	122,912
Non-vested common shares forfeited	1,815	1,556
Stock options exercised	243,238	100,991
Shares tendered in payment of option price and income tax withholding amounts	87,933	37,397
Retained earnings
Cash dividends declared:
Common (in dollars per share)	0.00	0.1200
Preferred (in dollars per share)	0.00%	6.75%

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Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investment securities:
Held-to-maturity, fair values	$ 220,115	$ 218,933
Stockholders' equity:
Nonvoting noncumulative preferred stock, par value
Nonvoting noncumulative preferred stock, authorized shares	100,000	100,000
Nonvoting noncumulative preferred stock, issued shares	0	0
Nonvoting noncumulative preferred stock, outstanding shares	0	0

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Commitments and Contingencies

3 Months Ended

Mar. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Commitments and Contingencies

In the normal course of business, the Company is involved in various claims and litigation. In the opinion of management, following consultation with legal counsel, the ultimate liability or disposition thereof is not expected to have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company.

The Company had commitments under construction contracts of $67 as of March 31, 2013.

The Company had commitments to purchase held-to-maturity municipal securities of $960 as of March 31, 2013.

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Document and Entity Information	3 Months Ended
	Mar. 31, 2013
Entity Registrant Name	FIRST INTERSTATE BANCSYSTEM INC
Entity Central Index Key	0000860413
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Amendment Flag	false
Class A Common Stock
Entity Common Stock, Shares Outstanding	18,424,252
Class B Common Stock
Entity Common Stock, Shares Outstanding	25,190,690

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Financial Instruments with Off-Balance Sheet Risk

3 Months Ended

Mar. 31, 2013

Financial Instruments with Off-Balance Sheet Risk [Abstract]

Financial Instruments with Off-Balance Sheet Risk

Financial Instruments with Off-Balance Sheet Risk

The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the commitment contract. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. At March 31, 2013, commitments to extend credit to existing and new borrowers approximated $1,176,789 which included $362,247 on unused credit card lines and $304,030 with commitment maturities beyond one year.

Standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. At March 31, 2013, the Company had outstanding standby letters of credit of $71,407. The estimated fair value of the obligation undertaken by the Company in issuing the standby letters of credit is included in other liabilities in the Company’s consolidated balance sheet.

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Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Interest income:
Interest and fees on loans	$ 55,493	$ 57,910
Interest and dividends on investment securities:
Taxable	8,046	9,705
Exempt from federal taxes	1,226	1,204
Interest on deposits in banks	298	237
Interest on federal funds sold	4	1
Total interest income	65,067	69,057
Interest expense:
Interest on deposits	4,355	6,262
Interest on securities sold under repurchase agreements	100	156
Interest on long-term debt	480	498
Interest on preferred stock pending redemption	159	0
Interest on subordinated debentures held by subsidiary trusts	696	1,507
Total interest expense	5,790	8,423
Net interest income	59,277	60,634
Provision for loan losses	500	11,250
Net interest income after provision for loan losses	58,777	49,384
Non-interest income:
Income from the origination and sale of loans	10,675	8,384
Other service charges, commissions and fees	8,256	8,424
Wealth management revenues	4,134	3,283
Service charges on deposit accounts	4,068	4,161
Investment securities gains, net	8	31
Other income	1,678	2,099
Total non-interest income	28,819	26,382
Non-interest expense:
Salaries and wages	23,405	21,564
Employee benefits	8,175	8,966
Occupancy, net	4,026	3,988
Furniture and equipment	3,052	3,138
Outsourced technology services	2,157	2,266
OREO expense, net of income	1,896	1,105
FDIC insurance premiums	1,377	1,595
Professional fees	1,127	933
Mortgage servicing rights amortization	839	895
Mortgage servicing rights impairment recovery	(48)	(868)
Core deposit intangibles amortization	354	355
Other expenses	10,325	13,503
Total non-interest expense	56,685	57,440
Income before income tax expense	30,911	18,326
Income tax expense	10,867	6,112
Net income	20,044	12,214
Preferred stock dividends	0	853
Net income available to common stockholders	$ 20,044	$ 11,361
Basic earnings per common share	$ 0.46	$ 0.26
Diluted earnings per common share	$ 0.46	$ 0.26

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Allowance For Loan Losses

3 Months Ended

Mar. 31, 2013

Receivables [Abstract]

Allowance For Loan Losses

Allowance For Loan Losses

The following tables present a summary of changes in the allowance for loan losses by portfolio segment for the periods indicated.

Three Months Ended March 31, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
Allowance for loan losses:
Beginning balance	$	75,782		$	7,140		$	17,073		$	504		$	12	$	100,511
Provision charged to operating expense	(1,035		)	537			1,015			(23		)	6		500
Less loans charged-off	(4,143		)	(1,062		)	(811		)	(4		)	—		(6,020		)
Add back recoveries of loans previously    charged-off	1,062			473			1,375			3			—		2,913
Ending balance	$	71,666		$	7,088		$	18,652		$	480		$	18	$	97,904
Loans individually evaluated for impairment	$	8,367		$	—		$	3,725		$	25		$	—	$	12,117
Loans collectively evaluated for impairment	63,299			7,088			14,927			455			18		85,787
Allowance for loan losses	$	71,666		$	7,088		$	18,652		$	480		$	18	$	97,904
Total loans:
Individually evaluated for impairment	$	114,690		$	—		$	15,832		$	152		$	—	$	130,674
Collectively evaluated for impairment	2,671,943			636,364			673,012			111,259			1,307		4,093,885
Total loans	$	2,786,633		$	636,364		$	688,844		$	111,411		$	1,307	$	4,224,559

Three Months Ended March 31, 2012	Real Estate			Consumer			Commercial			Agriculture			Other		Total
Allowance for loan losses:
Beginning balance	$	87,396		$	8,594		$	15,325		$	1,266		$	—	$	112,581
Provision charged to operating expense	6,382			(591		)	5,441			18			—		11,250
Less loans charged-off	(5,156		)	(1,312		)	(2,512		)	(107		)	—		(9,087		)
Add back recoveries of loans previously    charged-off	506			521			126			5			—		1,158
Ending balance	$	89,128		$	7,212		$	18,380		$	1,182		$	—	$	115,902

Loans individually evaluated for impairment	$	26,673	$	—	$	4,126	$	491	$	—	$	31,290
Loans collectively evaluated for impairment	62,455		7,212		14,254		691		—		84,612
Allowance for loan losses	$	89,128	$	7,212	$	18,380	$	1,182	$	—	$	115,902
Total loans:
Individually evaluated for impairment	$	198,033	$	—	$	13,559	$	1,514	$	—	$	213,106
Collectively evaluated for impairment	2,516,946		606,073		694,838		127,085		568		3,945,510
Total loans	$	2,714,979	$	606,073	$	708,397	$	128,599	$	568	$	4,158,616

The Company performs a quarterly assessment of the adequacy of its allowance for loan losses in accordance with generally accepted accounting principles. The methodology used to assess the adequacy is consistently applied to the Company's loan portfolio and consists of three elements: (1) specific valuation allowances based on probable losses on impaired loans; (2) historical valuation allowances based on loan loss experience for similar loans with similar characteristics and trends; and (3) general valuation allowances determined based on changes in the nature of the loan portfolio, overall portfolio quality, industry concentrations, delinquency trends, general economic conditions and other qualitative risk factors both internal and external to the Company.

Specific allowances are established for loans where management has determined that probability of a loss exists by analyzing the borrower’s ability to repay amounts owed, collateral deficiencies and any relevant qualitative or economic factors impacting the loan. Historical valuation allowances are determined by applying percentage loss factors to the credit exposures from outstanding loans. For commercial, agricultural and real estate loans, loss factors are applied based on the internal risk classifications of these loans. For consumer loans, loss factors are applied on a portfolio basis. For commercial, agriculture and real estate loans, loss factor percentages are based on a migration analysis of our historical loss experience, designed to account for credit deterioration. For consumer loans, loss factor percentages are based on a one-year loss history. General valuation allowances are determined by evaluating, on a quarterly basis, changes in the nature and volume of the loan portfolio, overall portfolio quality, industry concentrations, current economic and regulatory conditions and the estimated impact of these factors on historical loss rates.

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Loans

3 Months Ended

Mar. 31, 2013

Receivables [Abstract]

Loans

Loans

The following table presents loans by class as of the dates indicated:

	March 31, 2013		December 31, 2012
Real estate loans:
Commercial	$	1,469,302	$	1,497,272
Construction:
Land acquisition & development	215,505		220,196
Residential	50,153		49,274
Commercial	65,228		65,059
Total construction loans	330,886		334,529
Residential	758,480		708,339
Agricultural	172,522		177,244
Total real estate loans	2,731,190		2,717,384
Consumer:
Indirect consumer	444,257		438,245
Other consumer	135,474		137,743
Credit card	56,633		60,806
Total consumer loans	636,364		636,794
Commercial	688,844		688,753
Agricultural	111,411		113,627
Other, including overdrafts	1,307		912
Loans held for investment	4,169,116		4,157,470
Mortgage loans held for sale	55,443		66,442
Total loans	$	4,224,559	$	4,223,912

Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The following tables present the contractual aging of the Company’s recorded investment in past due loans by class as of the period indicated:

							Total Loans
	30 - 59		60 - 89		> 90		30 or More
	Days		Days		Days		Days		Current		Non-accrual		Total
As of March 31, 2013	Past Due		Past Due		Past Due		Past Due		Loans		Loans		Loans
Real estate
Commercial	$	12,846	$	865	$	—	$	13,711	$	1,410,640	$	44,951	$	1,469,302
Construction:
Land acquisition & development	6,294		62		—		6,356		192,376		16,773		215,505
Residential	92		—		—		92		48,726		1,335		50,153
Commercial	2,173		—		—		2,173		56,572		6,483		65,228
Total construction loans	8,559		62		—		8,621		297,674		24,591		330,886
Residential	4,269		502		1,044		5,815		744,108		8,557		758,480
Agricultural	1,464		349		2		1,815		166,116		4,591		172,522
Total real estate loans	27,138		1,778		1,046		29,962		2,618,538		82,690		2,731,190
Consumer:
Indirect consumer	2,166		326		3		2,495		441,477		285		444,257
Other consumer	642		157		1		800		133,786		888		135,474
Credit card	308		222		467		997		55,614		22		56,633
Total consumer loans	3,116		705		471		4,292		630,877		1,195		636,364
Commercial	4,097		3,966		329		8,392		665,884		14,568		688,844
Agricultural	813		311		95		1,219		110,051		141		111,411
Other, including overdrafts			—		—		—		1,307		—		1,307
Loans held for investment	35,164		6,760		1,941		43,865		4,026,657		98,594		4,169,116
Mortgage loans originated for sale	—		—		—		—		55,443		—		55,443
Total loans	$	35,164	$	6,760	$	1,941	$	43,865	$	4,082,100	$	98,594	$	4,224,559

							Total Loans
	30 - 59		60 - 89		> 90		30 or More
	Days		Days		Days		Days		Current		Non-accrual		Total
As of December 31, 2012	Past Due		Past Due		Past Due		Past Due		Loans		Loans		Loans
Real estate
Commercial	$	5,449	$	3,163	$	2	$	8,614	$	1,438,142	$	50,516	$	1,497,272
Construction:
Land acquisition & development	3,371		2,121		318		5,810		195,077		19,309		220,196
Residential	283		—		—		283		46,816		2,175		49,274
Commercial	—		—		—		—		56,933		8,126		65,059
Total construction loans	3,654		2,121		318		6,093		298,826		29,610		334,529
Residential	3,896		969		1,085		5,950		691,963		10,426		708,339
Agricultural	1,187		—		218		1,405		171,009		4,830		177,244
Total real estate loans	14,186		6,253		1,623		22,062		2,599,940		95,382		2,717,384
Consumer:
Indirect consumer	3,218		512		32		3,762		434,200		283		438,245
Other consumer	1,044		104		31		1,179		135,574		990		137,743
Credit card	409		278		392		1,079		59,704		23		60,806
Total consumer loans	4,671		894		455		6,020		629,478		1,296		636,794
Commercial	5,463		1,064		216		6,743		671,414		10,596		688,753
Agricultural	1,710		361		—		2,071		111,031		525		113,627
Other, including overdrafts	—		—		—		—		912		—		912
Loans held for investment	26,030		8,572		2,294		36,896		4,012,775		107,799		4,157,470
Mortgage loans originated for sale	—		—		—		—		66,442		—		66,442
Total loans	$	26,030	$	8,572	$	2,294	$	36,896	$	4,079,217	$	107,799	$	4,223,912

If interest on non-accrual loans had been accrued, such income would have approximated $1,352 and $2,702 for the three months ended March 31, 2013 and 2012, respectively.

The Company considers impaired loans to include all loans risk rated doubtful, loans placed on non-accrual status and loans renegotiated in troubled debt restructurings with the exception of consumer loans. The following tables present information on the Company’s recorded investment in impaired loans as of dates indicated:

As of March 31, 2013	Unpaid Total Principal Balance		Recorded Investment With No Allowance		Recorded Investment With Allowance		Total Recorded Investment		Related Allowance
Real estate:
Commercial	$	82,456	$	34,042	$	38,695	$	72,737	$	4,429
Construction:
Land acquisition & development	25,929		13,976		6,560		20,536		1,703
Residential	1,925		1,335		—		1,335		—
Commercial	9,422		6,227		256		6,483		68
Total construction loans	37,276		21,538		6,816		28,354		1,771
Residential	11,649		6,181		2,595		8,776		1,132
Agricultural	5,415		1,724		3,098		4,822		1,035
Total real estate loans	136,796		63,485		51,204		114,689		8,367
Commercial	16,521		7,969		7,863		15,832		3,725
Agricultural	205		127		25		152		25
Total	$	153,522	$	71,581	$	59,092	$	130,673	$	12,117

As of December 31, 2012	Unpaid Total Principal Balance		Recorded Investment With No Allowance		Recorded Investment With Allowance		Total Recorded Investment		Related Allowance
Real estate:
Commercial	$	84,300	$	39,049	$	34,774	$	73,823	$	4,112
Construction:
Land acquisition & development	28,558		15,891		7,173		23,064		1,457
Residential	3,018		1,976		710		2,686		251
Commercial	10,447		7,785		340		8,125		69
Total construction loans	42,023		25,652		8,223		33,875		1,777
Residential	13,271		6,152		4,495		10,647		1,677
Agricultural	5,559		1,834		3,227		5,061		784
Total real estate loans	145,153		72,687		50,719		123,406		8,350
Commercial	12,770		9,036		3,206		12,242		1,919
Agricultural	589		509		28		537		28
Total	$	158,512	$	82,232	$	53,953	$	136,185	$	10,297

The following table presents the average recorded investment in and income recognized on impaired loans for the periods indicated:

	Three Months Ended March 31,
	2013				2012
	Average Recorded Investment		Income Recognized		Average Recorded Investment		Income Recognized
Real estate:
Commercial	$	73,936	$	338	$	88,657	$	188
Construction:
Land acquisition & development	22,641		441		62,227		3
Residential	2,259		—		9,208		18
Commercial	7,898		—		24,265		—
Total construction loans	32,798		441		95,700		21
Residential	10,519		4		18,072		160
Agricultural	4,948		4		7,268		56
Total real estate loans	122,201		787		209,697		425
Commercial	12,746		18		17,885		31
Agricultural	632		4		1,234		—
Total	$	135,579	$	809	$	228,816	$	456

The amount of interest income recognized by the Company within the period that the loans were impaired was primarily related to loans modified in a troubled debt restructuring that remained on accrual status. Interest payments received on non-accrual impaired loans are applied to principal. Interest income is subsequently recognized only to the extent cash payments are received in excess of principal due. If interest on impaired loans had been accrued, interest income on impaired loans would have been approximately $1,335 and $2,683 for the three months ended March 31, 2013 and 2012, respectively.

Collateralized impaired loans are generally recorded at the fair value of the underlying collateral using discounted cash flows, independent appraisals and management estimates based upon current market conditions. For loans measured under the present value of cash flows method, the change in present value attributable to the passage of time, if applicable, is recognized in the provision for loan losses and thus no interest income is recognized.

Modifications of performing loans are made in the ordinary course of business and are completed on a case-by-case basis as negotiated with the borrower. Loan modifications typically include interest rate concessions, interest only periods of less than twelve months, short-term payment deferrals and extension of amortization periods to provide payment relief. A loan modification is considered a troubled debt restructuring if the borrower is experiencing financial difficulties and the Company, for economic or legal reasons, grants a concession to the borrower that it would not otherwise consider. Certain troubled debt restructurings are on non-accrual status at the time of restructuring and are typically returned to accrual status after considering the borrower's sustained repayment performance in accordance with the restructuring agreement for a period of at least six months and management is reasonably assured of future performance. If the troubled debt restructuring meets these performance criteria and the interest rate granted at the modification is equal to or greater than the rate that the Company was willing to accept at the time of the restructuring for a new loan with comparable risk, then the loan will return to performing status and the accrual of interest will resume.

The Company had loans renegotiated in troubled debt restructurings of $75,229 as of March 31, 2013, of which $39,442 were included in non-accrual loans and $35,787 were on accrual status. The Company had loans renegotiated in troubled debt restructurings of $76,597 as of December 31, 2012, of which $44,665 were included in non-accrual loans and $31,932 were on accrual status.

The following table presents information on the Company's troubled debt restructurings that occurred during the three months ended March 31, 2013:    

	Number of Notes	Type of Concession								Principal Balance at Restructure Date
Three Months Ended March 31, 2013		Interest only period		Extension of terms or maturity		Interest rate adjustment		Other (1)
Real estate:
Commercial	11	$	120	$	389	$	5,345	$	183	$	6,037
Total real estate loans	11	120		389		5,345		183		6,037
Commercial	4	50		178		265		87		580
Total loans restructured during period	15	$	170	$	567	$	5,610	$	270	$	6,617

(1) Other includes concessions that reduce or defer payments for a specified period of time and/or do not fit into other designated categories.

For troubled debt restructurings that were on non-accrual status or otherwise deemed impaired before the modification, a specific reserve may already be recorded. In periods subsequent to modification, the Company continues to evaluate all troubled debt restructurings for possible impairment and recognizes impairment through the allowance. Additionally these loans continue to work their way through the credit cycle through charge-off, pay-off or foreclosure. Financial effects of modifications of troubled debt restructurings may include principal loan forgiveness or other charge-offs directly related to the restructuring. The Company had no charge-offs directly related to modifying troubled debt restructurings during the three months ended March 31, 2013 or 2012.

The following table presents information on the Company's troubled debt restructurings during the previous 12 months for which there was a payment default during the periods indicated. The Company considers a payment default to occur on troubled debt restructurings when the loan is 90 days or more past due or was placed on non-accrual status after the modification.

	Three Months Ended March 31,
	Number of Notes	Balance
Residential real estate	1	$	278
Commercial	1	372
Total	2	$	650

At March 31, 2013, there were no material commitments to lend additional funds to borrowers whose existing loans have been renegotiated or are classified as non-accrual.

As part of the on-going and continuous monitoring of the credit quality of the Company’s loan portfolio, management tracks internally assigned risk classifications of loans. The Company adheres to a Uniform Classification System developed jointly by the various bank regulatory agencies to internally risk rate loans. The Uniform Classification System defines three broad categories of criticized assets, which the Company uses as credit quality indicators:

Other Assets Especially Mentioned — includes loans that exhibit weaknesses in financial condition, loan structure or documentation, which if not promptly corrected, may lead to the development of abnormal risk elements.

Substandard — includes loans that are inadequately protected by the current sound worth and paying capacity of the borrower. Although the primary source of repayment for a Substandard is not currently sufficient; collateral or other sources of repayment are sufficient to satisfy the debt. Continuance of a Substandard loan is not warranted unless positive steps are taken to improve the worthiness of the credit.

Doubtful — includes loans that exhibit pronounced weaknesses to a point where collection or liquidation in full, on the basis of currently existing facts, conditions and values, is highly questionable and improbable. Doubtful loans are required to be placed on non-accrual status and are assigned specific loss exposure.

The following tables present the Company’s recorded investment in criticized loans by class and credit quality indicator based on the most recent analysis performed as of the dates indicated:

As of March 31, 2013	Other Assets Especially Mentioned		Substandard		Doubtful		Total Criticized Loans
Real estate:
Commercial	$	89,207	$	127,083	$	16,110	$	232,400
Construction:
Land acquisition & development	29,171		22,977		4,231		56,379
Residential	2,132		1,728		801		4,661
Commercial	3,000		695		5,788		9,483
Total construction loans	34,303		25,400		10,820		70,523
Residential	9,890		11,185		2,981		24,056
Agricultural	19,062		6,705		3,097		28,864
Total real estate loans	152,462		170,373		33,008		355,843
Consumer:
Indirect consumer	704		1,660		79		2,443
Other consumer	587		1,120		436		2,143
Credit card	—		447		2,281		2,728
Total consumer loans	1,291		3,227		2,796		7,314
Commercial	41,399		22,072		7,996		71,467
Agricultural	2,493		1,423		25		3,941
Total	$	197,645	$	197,095	$	43,825	$	438,565

As of December 31, 2012	Other Assets Especially Mentioned		Substandard		Doubtful		Total Criticized Loans
Real estate:
Commercial	$	101,936	$	135,282	$	15,173	$	252,391
Construction:
Land acquisition & development	28,137		25,884		4,739		58,760
Residential	2,531		2,427		1,143		6,101
Commercial	3,000		795		7,383		11,178
Total construction loans	33,668		29,106		13,265		76,039
Residential	9,542		11,680		4,511		25,733
Agricultural	18,490		6,737		3,228		28,455
Total real estate loans	163,636		182,805		36,177		382,618
Consumer:
Indirect consumer	793		1,764		114		2,671
Other consumer	684		1,395		628		2,707
Credit card	—		415		2,085		2,500
Total consumer loans	1,477		3,574		2,827		7,878
Commercial	42,223		27,184		3,428		72,835
Agricultural	2,596		1,625		28		4,249
Total	$	209,932	$	215,188	$	42,460	$	467,580

The Company maintains a credit review function, which is independent of the credit approval process, to assess assigned internal risk classifications and monitor compliance with internal lending policies and procedures. Written action plans with firm target dates for resolution of identified problems are maintained and reviewed on a quarterly basis for all categories of criticized loans.

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Subsequent Events

3 Months Ended

Mar. 31, 2013

Subsequent Events [Abstract]

Subsequent Events

Subsequent Events

Subsequent events have been evaluated for potential recognition and disclosure through the date financial statements were filed with the Securities and Exchange Commission. On April 25, 2013, the Executive Committee of the Company's Board of Directors declared a quarterly dividend to common shareholders of $0.13 per share, to be paid on May 15, 2013 to shareholders of record as of May 6, 2013. No other events requiring recognition or disclosure were identified.

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Supplemental Disclosures to Consolidated Statement of Cash Flows

3 Months Ended

Mar. 31, 2013

Supplemental Cash Flow Information [Abstract]

Supplemental Disclosures to Consolidated Statement of Cash Flows

Supplemental Disclosures to Consolidated Statement of Cash Flows

The Company transferred loans of $5,331 and $13,978 to OREO during the three months endedMarch 31, 2013 and 2012, respectively.

The Company transferred internally originated mortgage servicing rights of $1,144 and $1,040 from loans to mortgage servicing assets during the three months endedMarch 31, 2013 and 2012, respectively.

The Company reclassified tax credit investments with a carrying value of $429 from held-to-maturity investment securities to other assets during the three months endedMarch 31, 2013.

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Earnings per Common Share

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Earnings per Common Share

Earnings per Common Share

Basic earnings per common share is calculated by dividing net income by the weighted average number of common shares outstanding during the period presented, excluding unvested restricted stock. Diluted earnings per share is calculated by dividing net income by the weighted average number of common shares determined for the basic earnings per share computation plus the dilutive effects of stock-based compensation using the treasury stock method.

The following table sets forth the computation of basic and diluted earnings per share for the three month periods ended March 31, 2013 and 2012.

	Three Months Ended March 31,
	2013		2012
Net income	$	20,044	$	12,214
Less preferred stock dividends	—		853
Net income available to common shareholders, basic and diluted	$	20,044	$	11,361
Weighted average common shares outstanding for basic earnings per share computation	43,140,409		42,873,769
Dilutive effects of stock-based compensation	287,973		108,774
Weighted average common shares outstanding for diluted earnings per common share computation	43,428,382		42,982,543
Basic earnings per common share	$	0.46	$	0.26
Diluted earnings per common share	$	0.46	$	0.26

The Company had 1,025,419 and 2,657,668 stock options outstanding as of March 31, 2013 and 2012, respectively, that were not included in the computation of diluted earnings per common share because their effect would be anti-dilutive. The Company had 61,760 and 48,196 shares of unvested restricted stock as of March 31, 2013 and 2012, respectively, that were not included in the computation of diluted earnings per common share because performance conditions for vesting had not been met.

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OREO

3 Months Ended

Mar. 31, 2013

Repossessed Assets [Abstract]

Other Real Estate Owned

Other Real Estate Owned

Information with respect to the Company's other real estate owned follows:

	Three Months Ended March 31,
	2013			2012
Beginning balance	$	32,571		$	37,452
Additions	5,331			13,978
Capitalized improvements	10			(331		)
Valuation adjustments	(2,305		)	(578		)
Dispositions	(3,137		)	(5,765		)
Ending balance	$	32,470		$	44,756

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Capital Stock

3 Months Ended

Mar. 31, 2013

Equity [Abstract]

Common Stock

Capital Stock

The Company had 18,424,252 and 17,635,369 shares of Class A common stock outstanding as of March 31, 2013 and December 31, 2012, respectively.

The Company had 25,190,690 and 25,654,954 shares of Class B common stock outstanding as of March 31, 2013 and December 31, 2012, respectively.

On December 31, 2012, the Company provides notice to holders of the Series A noncummulative redeemable preferred stock ("Series A Preferred Stock") of its intention to redeem the Series A Preferred Stock on January 18, 2013. Upon notice to holders of the redemption, the Series A Preferred Stock was reclassified from stockholders' equity to a liability. The aggregate redemption price for the Series A Preferred Stock was $50,150.

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Regulatory Capital

3 Months Ended

Mar. 31, 2013

Banking and Thrift [Abstract]

Regulatory Capital

Regulatory Capital

The Company is subject to the regulatory capital requirements administered by federal banking regulators and the Federal Reserve. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company must meet specific capital guidelines that involve quantitative measures of the Company’s assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. Quantitative measures established by regulation to ensure capital adequacy require the Company to maintain minimum amounts and ratios of total and tier 1 capital to risk-weighted assets, and of tier 1 capital to average assets, as defined in the regulations. As of March 31, 2013 and December 31, 2012, the Company exceeded all capital adequacy requirements to which it is subject.

Actual capital amounts and ratios and selected minimum regulatory thresholds for the Company and its bank subsidiary, First Interstate Bank (“FIB”), as of March 31, 2013 and December 31, 2012 are presented in the following tables:

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
March 31, 2013
Total risk-based capital:
Consolidated	$	766,478	15.9	%	$	385,443	8.0	%	NA		NA
FIB	707,053		14.7		383,593		8.0		$	479,491	10.0	%
Tier 1 risk-based capital:
Consolidated	677,787		14.1		192,721		4.0		NA		NA
FIB	634,648		13.2		191,796		4.0		$	287,695	6.0
Leverage capital ratio:
Consolidated	677,787		9.2		293,323		4.0		NA		NA
FIB	634,648		8.7		292,739		4.0		$	365,924	5.0

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
December 31, 2012
Total risk-based capital:
Consolidated	$	748,431	15.6	%	$	384,014	8.0	%	NA		NA
FIB	697,695		14.6		382,245		8.0		$	477,806	10.0	%
Tier 1 risk-based capital:
Consolidated	652,929		13.6		192,007		4.0		NA		NA
FIB	622,466		13.0		191,122		4.0		$	286,683	6.0
Leverage capital ratio:
Consolidated	652,929		8.8		296,559		4.0		NA		NA
FIB	622,466		8.4		296,061		4.0		$	370,077	5.0

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Investment Securities Gross Unrealized Losses and Fair Values of Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013 securities	Dec. 31, 2012 securities
Available-for-Sale:
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 548,138	$ 344,180
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	(3,843)	(1,689)
Available-for-Sale, 12 Months or More Fair Value	125	137
Available-for-Sale, 12 Months or More Gross Unrealized Losses	(1)	(1)
Available-for-Sale, Total Fair Value	548,263	344,317
Available-for-Sale, Total Gross Unrealized Losses	(3,844)	(1,690)
Held-to-Maturity:
Held-to-Maturity, Less than 12 Months Fair Value	27,427	28,701
Held-to-Maturity, Less than 12 Months Gross Unrealized Losses	(282)	(181)
Held-to-Maturity, 12 Months or More Fair Value	525	557
Held-to-Maturity, 12 Months or More Gross Unrealized Losses	(6)	(8)
Held-to-Maturity, Total Fair Value	27,952	29,258
Held-to-Maturity, Total Gross Unrealized Losses	(288)	(189)
Available-for-Sale and Held-to-Maturity:
Investment Securities in an Unrealized Loss Position (Number of Securities)	91	69
Obligations of U.S. government agencies
Available-for-Sale:
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	182,957	93,982
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	(342)	(163)
Available-for-Sale, 12 Months or More Fair Value	0	0
Available-for-Sale, 12 Months or More Gross Unrealized Losses	0	0
Available-for-Sale, Total Fair Value	182,957	93,982
Available-for-Sale, Total Gross Unrealized Losses	(342)	(163)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations
Available-for-Sale:
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	365,181	250,198
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	(3,501)	(1,526)
Available-for-Sale, 12 Months or More Fair Value	0	0
Available-for-Sale, 12 Months or More Gross Unrealized Losses	0	0
Available-for-Sale, Total Fair Value	365,181	250,198
Available-for-Sale, Total Gross Unrealized Losses	(3,501)	(1,526)
Private mortgage-backed securities
Available-for-Sale:
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	0	0
Available-for-Sale, 12 Months or More Fair Value	125	137
Available-for-Sale, 12 Months or More Gross Unrealized Losses	(1)	(1)
Available-for-Sale, Total Fair Value	125	137
Available-for-Sale, Total Gross Unrealized Losses	(1)	(1)
State, county and municipal securities
Held-to-Maturity:
Held-to-Maturity, Less than 12 Months Fair Value	24,188	19,389
Held-to-Maturity, Less than 12 Months Gross Unrealized Losses	(276)	(168)
Held-to-Maturity, 12 Months or More Fair Value	525	557
Held-to-Maturity, 12 Months or More Gross Unrealized Losses	(6)	(8)
Held-to-Maturity, Total Fair Value	24,713	19,946
Held-to-Maturity, Total Gross Unrealized Losses	(282)	(176)
Corporate Debt Securities [Member]
Held-to-Maturity:
Held-to-Maturity, Less than 12 Months Fair Value	3,239	9,312
Held-to-Maturity, Less than 12 Months Gross Unrealized Losses	(6)	(13)
Held-to-Maturity, 12 Months or More Fair Value	0	0
Held-to-Maturity, 12 Months or More Gross Unrealized Losses	0	0
Held-to-Maturity, Total Fair Value	3,239	9,312
Held-to-Maturity, Total Gross Unrealized Losses	$ (6)	$ (13)

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Schedule of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring and Non-Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
OREO expense, net of income	$ 1,896	$ 1,105
Related Allowance	12,117		10,297
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Non-recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0		0
Other real estate owned	0		0
Long-lived assets to be disposed of by sale	0		0
Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights	18,807		16,373
Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Non-recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0		0
Other real estate owned	0		0
Long-lived assets to be disposed of by sale	0		0
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights	0		0
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	77,089		74,623
Other real estate owned	14,372		15,745
Long-lived assets to be disposed of by sale	496
OREO expense, net of income	2,305	578
Related Allowance	(12,117)		(10,297)
Impaired Financing Receivable, Related Allowance, Partial Loan Charge-Offs	(22,848)		(22,327)
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis | Directly Related to Receipt of Updated Appraisals and Adjustments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
OREO expense, net of income		511
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis | Based on Management Estimates of the Current Fair Value of Properties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
OREO expense, net of income		67
Estimated Fair Value | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights	18,807		16,373
Estimated Fair Value | Fair Value Measured on a Non-recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	77,089		74,623
Other real estate owned	14,372		15,745
Long-lived assets to be disposed of by sale	496		496
Change During Period | Fair Value Measured on a Non-recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets to be disposed of by sale	70
Obligations of U.S. government agencies | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
Obligations of U.S. government agencies | Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	779,922		754,856
Obligations of U.S. government agencies | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
Obligations of U.S. government agencies | Estimated Fair Value | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	779,922		754,856
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	1,230,738		1,239,851
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Estimated Fair Value | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	1,230,738		1,239,851
Private mortgage-backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
Private mortgage-backed securities | Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	509		551
Private mortgage-backed securities | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
Private mortgage-backed securities | Estimated Fair Value | Fair Value Measured on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	509		551
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	2,011,169		1,995,258
Mortgage servicing rights	18,807		16,373
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
Mortgage servicing rights	0		0
Estimated Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	2,011,169		1,995,258
Mortgage servicing rights	18,807		16,373
Estimated Fair Value | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0		0
Mortgage servicing rights	0		0
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	77,089		74,623
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	2,011,169		1,995,258
Mortgage servicing rights	13,006		12,653
Carrying Amount | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	112,054		107,247
Long-lived assets to be disposed of by sale	$ 566

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Fair Value Measurements

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Fair Value Measurements

Fair Value Measurements

Financial assets and financial liabilities measured at fair value on a recurring basis are as follows:

			Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale:
Obligations of U.S. government agencies	$	779,922	$	—	$	779,922	$	—
U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,230,738		—		1,230,738		—
Private mortgage-backed securities	509		—		509		—
Mortgage servicing rights	18,807		—		18,807		—

			Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale:
Obligations of U.S. government agencies	$	754,856	$	—	$	754,856	$	—
U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,239,851		—		1,239,851		—
Private mortgage-backed securities	551		—		551		—
Mortgage servicing rights	16,373		—		16,373		—

There were no transfers between levels of the fair value hierarchy during the three months endedMarch 31, 2013 or 2012.

The methodologies used by the Company in determining the fair values of each class of financial instruments are based primarily on the use of independent, market-based data to reflect a value that would be reasonably expected in an orderly transaction between market participants at the measurement date. The Company obtains fair value measurements for investment securities from an independent pricing service and evaluates mortgage servicing rights for impairment using an independent valuation service. The vendors chosen by the Company are widely recognized vendors whose evaluations support the pricing functions of financial institutions, investment and mutual funds, and portfolio managers. The Company has documented and evaluated the pricing methodologies used by the vendors and maintains internal processes that regularly test valuations. These internal processes include obtaining and reviewing available reports on internal controls, evaluating the prices for reasonableness given market changes, obtaining and evaluating the inputs used in the model for a sample of securities, investigating anomalies and confirming determinations through discussions with the vendor. For investment securities, if needed, a broker may be utilized to determine the reported fair value. Further details on the methods used to estimate the fair value of each class of financial instruments above are discussed below:

Investment Securities Available-for-Sale. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the investment's terms and conditions, among other things.

Mortgage Servicing Rights. Mortgage servicing rights are initially recorded at fair value based on comparable market quotes and are amortized in proportion to and over the period of estimated net servicing income. Mortgage servicing rights are evaluated quarterly for impairment using an independent valuation service. The valuation service utilizes discounted cash flow modeling techniques, which consider observable data that includes market consensus prepayment speeds and the predominant risk characteristics of the underlying loans including loan type, note rate and loan term. Management believes the significant inputs utilized in the valuation model are observable in the market.

Additionally, from time to time, certain assets are measured at fair value on a non-recurring basis. Adjustments to fair value generally result from the application of lower-of-cost-or-market accounting or write-downs of individual assets due to impairment.

The following table presents information about the Company’s assets and liabilities measured at fair value on a non-recurring basis.

			Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Impaired loans	$	77,089	$	—	$	—	$	77,089
Other real estate owned	14,372		—		—		14,372
Long-lived assets to be disposed of by sale	496		—		—		496
			Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Balance		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Impaired loans	$	74,623	$	—	$	—	$	74,623
Other real estate owned	15,745		—		—		15,745
Long-lived assets to be disposed of by sale	496		—		—		496

Impaired Loans. Collateralized impaired loans are reported at the fair value of the underlying collateral if repayment is expected solely from collateral. The impaired loans are reported at fair value through specific valuation allowance allocations. In addition, when it is determined that the fair value of an impaired loan is less than the recorded investment in the loan, the carrying value of the loan is adjusted to fair value through a charge to the allowance for loan losses. Collateral values are estimated using independent appraisals and management estimates of current market conditions. As of March 31, 2013, certain impaired loans with a carrying value of $112,054 were reduced by specific valuation allowance allocations of $12,117 and partial loan charge-offs of $22,848 resulting in a reported fair value of $77,089. As of December 31, 2012, certain impaired loans with a carrying value of $107,247 were reduced by specific valuation allowance allocations of $10,297 and partial loan charge-offs of $22,327 resulting in a reported fair value of $74,623.

OREO.The fair values of OREO are estimated using independent appraisals and management estimates of current market conditions. Upon initial recognition, write-downs based on the foreclosed asset's fair value at foreclosure are reported through charges to the allowance for loan losses. Periodically, the fair value of foreclosed assets is remeasured with any subsequent write-downs charged to OREO expense in the period in which they are identified. Write-downs of $2,305 during the three months ended March 31, 2013 were based on management estimates of the current fair value of properties. Write-downs of $578 during the three months ended March 31, 2012 included adjustments of $511 directly related to receipt of updated appraisals and $67 based on management estimates of the current fair value of properties.

Long-lived Assets to be Disposed of by Sale. Long-lived assets to be disposed of by sale are carried at the lower of carrying value or fair value less estimated costs to sell. The fair values of long-lived assets to be disposed of by sale are based upon observable market data and management estimates of current market conditions. As of March 31, 2013 and December 31, 2012, the Company had a long-lived asset to be disposed of by sale with a carrying value of $566 that had been reduced by write-downs of $70 resulting in a reported fair value of $496.

In addition, mortgage loans held for sale are required to be measured at the lower of cost or fair value. The fair value of mortgage loans held for sale is based upon binding contracts or quotes or bids from third party investors. As of March 31, 2013 and December 31, 2012, all mortgage loans held for sale were recorded at cost.

The Company is required to disclose the fair value of financial instruments for which it is practical to estimate fair value. The methodologies for estimating the fair value of financial instruments that are measured at fair value on a recurring or non-recurring basis are discussed above. The methodologies for estimating the fair value of other financial instruments are discussed below. For financial instruments bearing a variable interest rate where no credit risk exists, it is presumed that recorded book values are reasonable estimates of fair value.

Financial Assets. Carrying values of cash, cash equivalents and accrued interest receivable approximate fair values due to the liquid and/or short-term nature of these instruments. Fair values for investment securities held-to-maturity are obtained from an independent pricing service, which considers observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the investment’s terms and conditions, among other things. Fair values of fixed rate loans and variable rate loans that reprice on an infrequent basis are estimated by discounting future cash flows using current interest rates at which similar loans with similar terms would be made to borrowers of similar credit quality. Carrying values of variable rate loans that reprice frequently, and with no change in credit risk, approximate the fair values of these instruments.

Financial Liabilities. The fair values of demand deposits, savings accounts, securities sold under repurchase agreements and accrued interest payable are the amounts payable on demand at the reporting date. The fair values of fixed-maturity certificates of deposit are estimated using external market rates currently offered for deposits with similar remaining maturities. The carrying values of the interest bearing demand notes to the United States Treasury are deemed an approximation of fair values due to the frequent repayment and repricing at market rates. The floating rate subordinated debenture, floating rate subordinated term loan, notes payable to the FHLB, fixed rate subordinated term debt, and capital lease obligation are estimated by discounting future cash flows using current rates for advances with similar characteristics. The carrying value of the preferred stock pending redemption approximated fair value due to the short-term nature of the instrument.

Commitments to Extend Credit and Standby Letters of Credit. The fair value of commitments to extend credit and standby letters of credit, based on fees currently charged to enter into similar agreements, is not significant.

The estimated fair values of financial instruments that are reported at amortized cost in the Company's consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, are as follows:

					Fair Value Measurements at Reporting Date Using
As of March 31, 2013	Carrying Amount		Estimated Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	$	498,543	$	498,543	$	—	$	498,543	$	—
Investment securities available-for-sale	2,011,169		2,011,169		—		2,011,169		—
Investment securities held-to-maturity	210,426		220,115		—		220,115		—
Accrued interest receivable	29,375		29,375		—		29,375		—
Mortgage servicing rights, net	13,006		18,807		—		18,807		—
Net loans	4,126,655		4,139,777		—		4,062,688		77,089
Total financial assets	$	6,889,174	$	6,917,786	$	—	$	6,840,697	$	77,089
Financial liabilities:
Total deposits, excluding time deposits	$	4,684,664	$	4,684,664	$	—	$	4,684,664	$	—
Time deposits	1,343,681		1,351,742		—		1,351,742		—
Securities sold under repurchase agreements	467,205		467,205		—		467,205		—
Other borrowed funds	8		8		—		8		—
Accrued interest payable	6,433		6,433		—		6,433		—
Long-term debt	37,150		34,887		—		34,887		—
Subordinated debentures held by subsidiary    trusts	82,477		66,080		—		66,080		—
Total financial liabilities	$	6,621,618	$	6,611,019	$	—	$	6,611,019	$	—

					Fair Value Measurements at Reporting Date Using
As of December 31, 2012	Carrying Amount		Estimated Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	$	801,332	$	801,332	$	—	$	801,332	$	—
Investment securities available-for-sale	1,995,258		1,995,258		—		1,995,258		—
Investment securities held-to-maturity	208,223		218,933		—		218,933		—
Accrued interest receivable	28,869		28,869		—		28,869		—
Mortgage servicing rights, net	12,653		16,373		—		16,373		—
Net loans	4,123,401		4,142,426		—		4,067,803		74,623
Total financial assets	$	7,169,736	$	7,203,191	$	—	$	7,128,568	$	74,623
Financial liabilities:
Total deposits, excluding time deposits	$	4,854,927	$	4,854,927	$	—	$	4,854,927	$	—
Time deposits	1,385,484		1,394,403		—		1,394,403		—
Securities sold under repurchase agreements	505,785		505,785		—		505,785		—
Other borrowed funds	32		32		—		32		—
Accrued interest payable	6,502		6,502		—		6,502		—
Long-term debt	37,160		35,104		—		35,104		—
Preferred stock pending redemption	50,000		50,000				50,000
Subordinated debentures held by subsidiary    trusts	82,477		62,409		—		62,409		—
Total financial liabilities	$	6,922,367	$	6,909,162	$	—	$	6,909,162	$	—

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Allowance for Loan Losses (Tables)

3 Months Ended

Mar. 31, 2013

Receivables [Abstract]

Schedule of Allowance for Loan Losses by Portfolio Segment

The following tables present a summary of changes in the allowance for loan losses by portfolio segment for the periods indicated.

Three Months Ended March 31, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
Allowance for loan losses:
Beginning balance	$	75,782		$	7,140		$	17,073		$	504		$	12	$	100,511
Provision charged to operating expense	(1,035		)	537			1,015			(23		)	6		500
Less loans charged-off	(4,143		)	(1,062		)	(811		)	(4		)	—		(6,020		)
Add back recoveries of loans previously    charged-off	1,062			473			1,375			3			—		2,913
Ending balance	$	71,666		$	7,088		$	18,652		$	480		$	18	$	97,904
Loans individually evaluated for impairment	$	8,367		$	—		$	3,725		$	25		$	—	$	12,117
Loans collectively evaluated for impairment	63,299			7,088			14,927			455			18		85,787
Allowance for loan losses	$	71,666		$	7,088		$	18,652		$	480		$	18	$	97,904
Total loans:
Individually evaluated for impairment	$	114,690		$	—		$	15,832		$	152		$	—	$	130,674
Collectively evaluated for impairment	2,671,943			636,364			673,012			111,259			1,307		4,093,885
Total loans	$	2,786,633		$	636,364		$	688,844		$	111,411		$	1,307	$	4,224,559

Three Months Ended March 31, 2012	Real Estate			Consumer			Commercial			Agriculture			Other		Total
Allowance for loan losses:
Beginning balance	$	87,396		$	8,594		$	15,325		$	1,266		$	—	$	112,581
Provision charged to operating expense	6,382			(591		)	5,441			18			—		11,250
Less loans charged-off	(5,156		)	(1,312		)	(2,512		)	(107		)	—		(9,087		)
Add back recoveries of loans previously    charged-off	506			521			126			5			—		1,158
Ending balance	$	89,128		$	7,212		$	18,380		$	1,182		$	—	$	115,902

Loans individually evaluated for impairment	$	26,673	$	—	$	4,126	$	491	$	—	$	31,290
Loans collectively evaluated for impairment	62,455		7,212		14,254		691		—		84,612
Allowance for loan losses	$	89,128	$	7,212	$	18,380	$	1,182	$	—	$	115,902
Total loans:
Individually evaluated for impairment	$	198,033	$	—	$	13,559	$	1,514	$	—	$	213,106
Collectively evaluated for impairment	2,516,946		606,073		694,838		127,085		568		3,945,510
Total loans	$	2,714,979	$	606,073	$	708,397	$	128,599	$	568	$	4,158,616

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Schedule of Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Change in net unrealized Gain during period:
Change in net unrealized gain during period, before tax amount	$ (5,717)	$ 755
Change in net unrealized gain during period, tax expense (benefit)	(2,250)	296
Change in net unrealized gain during period, net of tax amount	(3,467)	459
Reclassification adjustment for gains included in net income:
Reclassification adjustment for gains included in net income, before tax amount	(8)	(31)
Reclassification adjustment for gains included in net income, tax expense (benefit)	(3)	(12)
Reclassification adjustment for gains included in net income, net of tax amount	(5)	(19)
Change in net actuarial loss:
Change in net actuarial loss, before tax amount	35	33
Change in net actuarial loss, tax expense (benefit)	14	13
Change in net actuarial loss, net of tax amount	21	20
Other comprehensive income (loss):
Other comprehensive income (loss), before tax	(5,690)	757
Total other comprehensive income, tax expense (benefit)	(2,239)	297
Total other comprehensive income, net of tax amount	$ (3,451)	$ 460

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Schedule of Allowance for Loan Losses by Portfolio Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 100,511	$ 112,581
Provision charged to operating expense	500	11,250
Less loans charged-off	(6,020)	(9,087)
Add back recoveries of loans previously charged-off	2,913	1,158
Ending balance	97,904	115,902
Allowance for loan losses:
Loans individually evaluated for impairment	12,117
Loans collectively evaluated for impairment	85,787
Ending balance	97,904	115,902
Total loans:
Individually evaluated for impairment	130,674
Individually evaluated for impairment	4,093,885
Total loans	4,224,559	4,158,616	4,223,912
Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	75,782	87,396
Provision charged to operating expense	(1,035)	6,382
Less loans charged-off	(4,143)	(5,156)
Add back recoveries of loans previously charged-off	1,062	506
Ending balance	71,666	89,128
Allowance for loan losses:
Loans individually evaluated for impairment	8,367
Loans collectively evaluated for impairment	63,299
Ending balance	71,666	89,128
Total loans:
Individually evaluated for impairment	114,690
Individually evaluated for impairment	2,671,943
Total loans	2,786,633	2,714,979
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	7,140	8,594
Provision charged to operating expense	537	(591)
Less loans charged-off	(1,062)	(1,312)
Add back recoveries of loans previously charged-off	473	521
Ending balance	7,088	7,212
Allowance for loan losses:
Loans individually evaluated for impairment	0
Loans collectively evaluated for impairment	7,088
Ending balance	7,088	7,212
Total loans:
Individually evaluated for impairment	0
Individually evaluated for impairment	636,364
Total loans	636,364	606,073
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	17,073	15,325
Provision charged to operating expense	1,015	5,441
Less loans charged-off	(811)	(2,512)
Add back recoveries of loans previously charged-off	1,375	126
Ending balance	18,652	18,380
Allowance for loan losses:
Loans individually evaluated for impairment	3,725
Loans collectively evaluated for impairment	14,927
Ending balance	18,652	18,380
Total loans:
Individually evaluated for impairment	15,832
Individually evaluated for impairment	673,012
Total loans	688,844	708,397
Agriculture
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	504	1,266
Provision charged to operating expense	(23)	18
Less loans charged-off	(4)	(107)
Add back recoveries of loans previously charged-off	3	5
Ending balance	480	1,182
Allowance for loan losses:
Loans individually evaluated for impairment	25
Loans collectively evaluated for impairment	455
Ending balance	480	1,182
Total loans:
Individually evaluated for impairment	152
Individually evaluated for impairment	111,259
Total loans	111,411	128,599
Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	12	0
Provision charged to operating expense	6	0
Less loans charged-off	0	0
Add back recoveries of loans previously charged-off	0	0
Ending balance	18	0
Allowance for loan losses:
Loans individually evaluated for impairment	0
Loans collectively evaluated for impairment	18
Ending balance	18	0
Total loans:
Individually evaluated for impairment	0
Individually evaluated for impairment	1,307
Total loans	$ 1,307	$ 568

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Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income	$ 20,044	$ 12,214
Other comprehensive income (loss), before tax:
Change in net unrealized gains (losses) during period	(5,717)	755
Reclassification adjustment for net gains included in income	(8)	(31)
Defined benefit post-retirement benefits plans:
Change in net actuarial loss	35	33
Other comprehensive income (loss), before tax	(5,690)	757
Deferred tax benefit (expense) related to other comprehensive income	2,239	(297)
Other comprehensive income (loss), net of tax	(3,451)	460
Comprehensive income, net of tax	$ 16,593	$ 12,674

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Investment Securities

3 Months Ended

Mar. 31, 2013

Investments, Debt and Equity Securities [Abstract]

Investment Securities

Investment Securities

The amortized cost and approximate fair values of investment securities are summarized as follows:

March 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-Sale:
Obligations of U.S. government agencies	$	777,044	$	3,220	$	(342	)	$	779,922
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,210,425		23,814		(3,501		)	1,230,738
Private mortgage-backed securities	495		15		(1		)	509
Total	$	1,987,964	$	27,049	$	(3,844	)	$	2,011,169

March 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Held-to Maturity:
State, county and municipal securities	$	192,241	$	9,881	$	(282	)	$	201,840
Corporate securities	18,185		96		(6		)	18,275
Total	$	210,426	$	9,977	$	(288	)	$	220,115

December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-Sale:
Obligations of U.S. government agencies	$	751,501	$	3,518	$	(163	)	$	754,856
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,214,377		27,000		(1,526		)	1,239,851
Private mortgage-backed securities	539		13		(1		)	551
Total	$	1,966,417	$	30,531	$	(1,690	)	$	1,995,258

December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Held-to Maturity:
State, county and municipal securities	$	192,875	$	10,835	$	(176	)	$	203,534
Corporate securities	14,975		64		(13		)	15,026
Other securities	373		—		—			373
Total	$	208,223	$	10,899	$	(189	)	$	218,933

Gross realized gains and losses from the disposition of investment securities are summarized in the following table:

	Three Months Ended March 31,
	2013		2012
Gross realized gains	$	8	$	31
Gross realized losses	—		—

The following tables show the gross unrealized losses and fair values of investment securities, aggregated by investment category, and the length of time individual investment securities have been in a continuous unrealized loss position, as of March 31, 2013 and December 31, 2012

	Less than 12 Months					12 Months or More					Total
March 31, 2013	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale:
Obligations of U.S. government agencies	$	182,957	$	(342	)	$	—	$	—		$	182,957	$	(342	)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	365,181		(3,501		)	—		—			365,181		(3,501		)
Private mortgage-backed securities	—		—			125		(1		)	125		(1		)
Total	$	548,138	$	(3,843	)	$	125	$	(1	)	$	548,263	$	(3,844	)

	Less than 12 Months					12 Months or More					Total
March 31, 2013	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Held-to-Maturity:
State, county and municipal securities	$	24,188	$	(276	)	$	525	$	(6	)	$	24,713	$	(282	)
Corporate securities	3,239		(6		)	—		—			3,239		(6		)
Total	$	27,427	$	(282	)	$	525	$	(6	)	$	27,952	$	(288	)

	Less than 12 Months					12 Months or More					Total
December 31, 2012	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale:
Obligations of U.S. government agencies	$	93,982	$	(163	)	$	—	$	—		$	93,982	$	(163	)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	250,198		(1,526		)	—		—			250,198		(1,526		)
Private mortgage-backed securities	—		—			137		(1		)	137		(1		)
Total	$	344,180	$	(1,689	)	$	137	$	(1	)	$	344,317	$	(1,690	)

	Less than 12 Months					12 Months or More					Total
December 31, 2012	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Held-to-Maturity:
State, county and municipal securities	$	19,389	$	(168	)	$	557	$	(8	)	$	19,946	$	(176	)
Corporate securities	9,312		(13		)	—		—			9,312		(13		)
Total	$	28,701	$	(181	)	$	557	$	(8	)	$	29,258	$	(189	)

The investment portfolio is evaluated quarterly for other-than-temporary declines in the market value of each individual investment security. The Company had 91 and 69 individual investment securities that were in an unrealized loss position as of March 31, 2013 and December 31, 2012, respectively. Unrealized losses as of March 31, 2013 and December 31, 2012 related primarily to fluctuations in the current interest rates. The Company does not have the intent to sell any of the available-for-sale securities in the above table and it is not likely that the Company will have to sell any such securities before a recovery in cost. No impairment losses were recorded during the three months ended March 31, 2013 and 2012.

Maturities of investment securities at March 31, 2013 are shown below. Maturities of mortgage-backed securities have been adjusted to reflect shorter maturities based upon estimated prepayments of principal. All other investment securities maturities are shown at contractual maturity dates.

	Available-for-Sale				Held-to-Maturity
March 31, 2013	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Within one year	$	400,147	$	405,641	$	3,877	$	3,925
After one year but within five years	1,127,952		1,141,233		52,321		53,266
After five years but within ten years	375,101		378,108		86,803		90,886
After ten years	84,764		86,187		67,425		72,038
Total	$	1,987,964	$	2,011,169	$	210,426	$	220,115

As of March 31, 2013, the Company had investment securities callable within one year with amortized costs and estimated fair values of $438,562 and $438,990, respectively, including callable structured notes with amortized costs and estimated fair values of $130,375 and $130,572, respectively. These investment securities are primarily classified as available-for-sale and included in the after one year but within five years category in the table above.

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OREO (Tables)

3 Months Ended

Mar. 31, 2013

Repossessed Assets [Abstract]

Other Real Estate Owned Roll Forward

Information with respect to the Company's other real estate owned follows:

	Three Months Ended March 31,
	2013			2012
Beginning balance	$	32,571		$	37,452
Additions	5,331			13,978
Capitalized improvements	10			(331		)
Valuation adjustments	(2,305		)	(578		)
Dispositions	(3,137		)	(5,765		)
Ending balance	$	32,470		$	44,756

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Loans Schedule of Recorded Investment in Impaired Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	$ 153,522		$ 158,512
Recorded Investment With No Allowance	71,581		82,232
Recorded Investment With Allowance	59,092		53,953
Total Recorded Investment	130,673		136,185
Related Allowance	12,117		10,297
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	135,579	228,816
Income Recognized	809	456
Interest Income on Impaired Loans If Interest Had Been Accrued	1,335	2,683
Commercial real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	82,456		84,300
Recorded Investment With No Allowance	34,042		39,049
Recorded Investment With Allowance	38,695		34,774
Total Recorded Investment	72,737		73,823
Related Allowance	4,429		4,112
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	73,936	88,657
Income Recognized	338	188
Land acquisition & development construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	25,929		28,558
Recorded Investment With No Allowance	13,976		15,891
Recorded Investment With Allowance	6,560		7,173
Total Recorded Investment	20,536		23,064
Related Allowance	1,703		1,457
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	22,641	62,227
Income Recognized	441	3
Residential construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	1,925		3,018
Recorded Investment With No Allowance	1,335		1,976
Recorded Investment With Allowance	0		710
Total Recorded Investment	1,335		2,686
Related Allowance	0		251
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	2,259	9,208
Income Recognized	0	18
Commercial construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	9,422		10,447
Recorded Investment With No Allowance	6,227		7,785
Recorded Investment With Allowance	256		340
Total Recorded Investment	6,483		8,125
Related Allowance	68		69
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	7,898	24,265
Income Recognized	0	0
Total construction loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	37,276		42,023
Recorded Investment With No Allowance	21,538		25,652
Recorded Investment With Allowance	6,816		8,223
Total Recorded Investment	28,354		33,875
Related Allowance	1,771		1,777
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	32,798	95,700
Income Recognized	441	21
Residential real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	11,649		13,271
Recorded Investment With No Allowance	6,181		6,152
Recorded Investment With Allowance	2,595		4,495
Total Recorded Investment	8,776		10,647
Related Allowance	1,132		1,677
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	10,519	18,072
Income Recognized	4	160
Agricultural real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	5,415		5,559
Recorded Investment With No Allowance	1,724		1,834
Recorded Investment With Allowance	3,098		3,227
Total Recorded Investment	4,822		5,061
Related Allowance	1,035		784
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	4,948	7,268
Income Recognized	4	56
Total real estate loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	136,796		145,153
Recorded Investment With No Allowance	63,485		72,687
Recorded Investment With Allowance	51,204		50,719
Total Recorded Investment	114,689		123,406
Related Allowance	8,367		8,350
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	122,201	209,697
Income Recognized	787	425
Commercial
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	16,521		12,770
Recorded Investment With No Allowance	7,969		9,036
Recorded Investment With Allowance	7,863		3,206
Total Recorded Investment	15,832		12,242
Related Allowance	3,725		1,919
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	12,746	17,885
Income Recognized	18	31
Agricultural
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	205		589
Recorded Investment With No Allowance	127		509
Recorded Investment With Allowance	25		28
Total Recorded Investment	152		537
Related Allowance	25		28
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	632	1,234
Income Recognized	$ 4	$ 0

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Other Comprehensive Income

3 Months Ended

Mar. 31, 2013

Equity [Abstract]

Other Comprehensive Income

Other Comprehensive Income

The gross amounts of each component of other comprehensive income and the related tax effects are as follows:

	Pre-tax						Tax Expense (Benefit)						Net of Tax
Three Months Ended March 31,	2013			2012			2013			2012			2013			2012
Investment securities available-for sale:
Change in net unrealized gain during period	$	(5,717	)	$	755		$	(2,250	)	$	296		$	(3,467	)	$	459
Reclassification adjustment for net gains included in net income	(8		)	(31		)	(3		)	(12		)	(5		)	(19		)
Defined benefits post-retirement benefit plan:
Change in net actuarial loss	35			33			14			13			21			20
Total other comprehensive income	$	(5,690	)	$	757		$	(2,239	)	$	297		$	(3,451	)	$	460

The components of accumulated other comprehensive income, net of income taxes, are as follows:

	March 31, 2013			December 31, 2012
Net unrealized gain on investment securities available-for-sale	$	14,065		$	17,537
Net actuarial loss on defined benefit post-retirement benefit plans	(1,525		)	(1,546		)
Net accumulated other comprehensive income	$	12,540		$	15,991