Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities
Net income		$ 116,127	$ 112,755	$ 95,644
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses		2,284	1,912	6,887
Net amortization of investment securities premiums and discounts		26,709	27,491	64,066
Loans held for sale originated or acquired		(888,676)	(669,144)	(918,451)
Proceeds from sales of loans held for sale		925,353	705,178	1,084,799
Gain on sale of loans		(26,389)	(19,797)	(28,517)
(Gain) loss on sale of investments		(19)	188	299
Bargain purchase gain		0	(680)	0
Stock-based compensation expense, net of tax benefits		1,087	859	1,011
Excess tax (benefits) deficiencies from stock-based compensation		(102)	(138)	223
Depreciation of premises and equipment		14,365	12,108	10,485
Loss (gain) on sale of other real estate owned and write-downs, net		938	(937)	1,450
Core deposit intangible amortization		2,964	2,811	2,401
Deferred tax (benefit) expense	[1]	(4,080)	5,931	4,633
Net (increase) decrease in accrued interest receivable		(2,377)	2,648	(265)
Net (increase) decrease in other assets		(793)	(5,702)	19,881
Net (decrease) increase in accrued interest payable		(828)	567	(1,354)
Net increase (decrease) in other liabilities		4,903	6,684	(9,097)
Net cash provided by operating activities		171,466	182,734	334,095
Investing Activities
Sales of available-for-sale securities		136,777	169,372	181,971
Maturities, prepayments and calls of available-for-sale securities		663,828	628,238	1,682,363
Purchases of available-for-sale securities		(961,224)	(281,332)	(1,426,262)
Maturities, prepayments and calls of held-to-maturity securities		20,997	8,930	0
Purchases of held-to-maturity securities		(203,554)	(49,691)	0
Principal collected on loans		1,737,508	1,418,517	1,224,222
Loans originated or acquired		(2,112,154)	(1,735,155)	(1,559,353)
Net addition of premises and equipment and other real estate owned		(18,224)	(14,389)	(8,977)
Proceeds from sale of other real estate owned		10,278	15,714	28,535
Net proceeds from sale of non-marketable equity securities		27,770	801	583
Net cash received (paid) in acquisitions		21,427	(2,112)	26,155
Net cash (used in) provided by investing activities		(676,571)	158,893	149,237
Financing Activities
Net increase (decrease) in deposits		215,650	455,604	(334,672)
Net increase in securities sold under agreements to repurchase		24,951	83,713	23,886
Net increase (decrease) in short-term Federal Home Loan Bank advances		140,000	(421,000)	(204,467)
Proceeds from long-term Federal Home Loan Bank advances		50,000	192,500	1,147,451
Repayments of long-term Federal Home Loan Bank advances		(94,749)	(314,738)	(1,105,282)
Net decrease in other borrowed funds		(566)	(933)	(1,502)
Cash dividends paid		(79,456)	(50,944)	(44,232)
Excess tax benefits (deficiencies) from stock-based compensation		102	138	(223)
Stock-based compensation activity		17	785	4,326
Net cash provided by (used in) financing activities		255,949	(54,875)	(514,715)
Net (decrease) increase in cash and cash equivalents		(249,156)	286,752	(31,383)
Cash and cash equivalents at beginning of period		442,409	155,657	187,040
Cash and cash equivalents at end of period		193,253	442,409	155,657
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest		30,103	26,398	30,111
Cash paid during the period for income taxes		39,622	33,343	23,576
Supplemental Disclosure of Non-Cash Investing Activities
Transfer of investment securities from available-for-sale to held-to-maturity		0	484,583	0
Sale and refinancing of other real estate owned		446	1,361	4,819
Transfer of loans to other real estate owned		7,989	11,493	15,266
Fair value of common stock shares issued		25,939	15,127	45,033
Cash consideration for outstanding shares		28,364	16,690	24,858
Fair value of assets acquired		434,963	349,167	630,569
Liabilities assumed		$ 391,592	$ 316,670	$ 560,678

[1] Includes tax benefit of operating loss carryforwards of $391,000, $0 and $0 for the years ended December 31, 2015, 2014, and 2013, respectively.