Acquisitions Schedule of Recognized Identifiable Assets Acquired and Liabilities Assumed (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended
	Jul. 31, 2014		Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			$ 35,972
Goodwill			205,574	183,673
Class A Common Stock
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	35,972
Mountain West Financial Corp Acquisition, As Recorded by MWFC
Business Acquisition [Line Items]
Cash and Cash Equivalents	74,035
Investment Securities	104,945
Loans	378,558
Allowance for Loan Losses	(11,598)
Premises and Equipment	35,283
Company Owned LIfe Insurance	13,046
Deferred Tax Assets, Net	6,491
Core Deposit Intangibles	0
Other Assets	16,559
Total Assets Acquired	617,319
Deposits	515,538
Other Liabilities	20,501
Subordinated Debentures Held by Subsidiary Trusts	20,439
Total Liabilities Assumed	556,478
Net Assets Acquired	60,841
Mountain West Bank Acquisition, Fair Value Adjustment
Business Acquisition [Line Items]
Cash and Cash Equivalents	0
Investment Securities	(34)	[1]
Loans	(18,286)	[2]
Allowance for Loan Losses	11,598	[3]
Premises and Equipment	(5,847)	[4]
Company Owned LIfe Insurance	0
Deferred Tax Assets, Net	1,135	[5]
Core Deposit Intangibles	11,014	[6]
Other Assets	(5,300)	[7]
Total Assets Acquired	(5,720)
Deposits	(159)	[8]
Other Liabilities	2,730	[9]
Subordinated Debentures Held by Subsidiary Trusts	0	[10]
Total Liabilities Assumed	2,571
Net Assets Acquired	(8,291)
Mountain West Bank Acquisition, As Recorded by the Company
Business Acquisition [Line Items]
Cash and Cash Equivalents	74,035
Investment Securities	104,911
Loans	360,272
Allowance for Loan Losses	0
Premises and Equipment	29,436
Company Owned LIfe Insurance	13,046
Deferred Tax Assets, Net	7,626
Core Deposit Intangibles	11,014
Other Assets	11,259
Total Assets Acquired	611,599
Deposits	515,379
Other Liabilities	23,231
Subordinated Debentures Held by Subsidiary Trusts	20,439
Total Liabilities Assumed	559,049
Net Assets Acquired	52,550
Payments to Acquire Businesses, Gross	38,479
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	35,972
Business Combination, Consideration Transferred	74,451
Goodwill	$ 21,901

[1] (1) Write down of the book value of investment securities to their estimated fair values on the date of acquisition based upon quotes obtained from an independent third party pricing service.

[2] (2) Write down of the book value of loans to their estimated fair values. Except for collateral dependent loans acquired with deteriorated credit quality, the fair value of loans was estimated using cash flow projections based on the remaining maturity and repricing terms, adjusted for estimated future credit losses and prepayments and discounted to present value using a risk-adjusted market rate for similar loans. The fair value of collateral dependent loans acquired with deteriorated credit quality was estimated based on the Company's analysis of the fair value of the each loan's underlying collateral, discounted using market-derived rates of return with consideration given to the period of time and costs associated with foreclosure and disposition of the collateral.

[3] (3) Adjustment to remove the MWB allowance for loan losses at acquisition date as the credit risk is accounted for in the fair value adjustment for loans receivable described in (2) above.

[4] (4) Write down of the book value of premises and equipment to their estimated fair values based upon appraisals obtained from an independent third party appraiser.

[5] (5) Adjustment represents the net deferred tax assets resulting from fair value adjustments related to acquired assets, assumed liabilities, core deposit intangible assets and other purchase accounting adjustments.

[6] (6) Adjustment represents the value of the core deposit base assumed in the acquisition based upon a valuation obtained from an independent third party valuation expert.

[7] (7) Adjustment consists of a reduction in the value of equity method investments and accrued interest receivable and the write-off of federal and state income taxes receivable, pre-existing goodwill and computer software costs.

[8] (8) Decrease in book value of time deposits to their estimated fair values based upon interest rates of similar time deposits with similar terms on the date of acquisition.

[9] (9) Adjustment represents increases in the book values of other liabilities to their estimated fair values at the acquisition date. The adjustment primarily consists of a $2,000 increase to an acquired capital lease obligation and a $473 increase to Federal Home Loan Bank borrowings based upon interest interest rates of similar obligations with similar characteristics on the date of acquisition.

[10] (10) Recorded value of junior subordinated debentures held by subsidiary trusts approximated fair value as of the acquisition date due to the short-term nature of the instruments. These debentures were redeemed at par value in December 2014.