Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets
Cash and due from banks	$ 128,976	$ 147,894
Federal funds sold	963	543
Interest bearing deposits in banks	507,864	650,233
Total cash and cash equivalents	637,803	798,670
Investment securities:
Available-for-sale	1,777,057	1,711,924
Held-to-maturity (estimated fair values of $576,931 and $584,533 at March 31, 2015 and December 31, 2014, respectively)	563,847	575,186
Total investment securities	2,340,904	2,287,110
Loans held for investment	4,871,548	4,856,615
Mortgage loans held for sale	55,758	40,828
Total loans	4,927,306	4,897,443
Less allowance for loan losses	75,336	74,200
Net loans	4,851,970	4,823,243
Goodwill	204,375	205,574
Premises and equipment, net of accumulated depreciation	192,748	195,212
Company-owned life insurance	154,741	153,821
Other real estate owned (OREO)	15,134	13,554
Accrued interest receivable	27,242	27,063
Core deposit intangibles, net of accumulated amortization	12,428	13,282
Mortgage servicing rights, net of accumulated amortization and impairment reserve	14,093	14,038
Deferred tax asset, net	0	4,874
Other assets	77,104	73,495
Total assets	8,528,542	8,609,936
Deposits:
Non-interest bearing	1,757,664	1,791,364
Interest bearing	5,210,495	5,214,848
Total deposits	6,968,159	7,006,212
Securities sold under repurchase agreements	462,073	502,250
Accounts payable and accrued expenses	49,665	66,164
Accrued interest payable	5,113	5,833
Deferred tax liability	3,553	0
Long-term debt	43,048	38,067
Other borrowed funds	4	9
Subordinated debentures held by subsidiary trusts	82,477	82,477
Total liabilities	7,614,092	7,701,012
Stockholders' equity:
Nonvoting noncumulative preferred stock without par value; authorized 100,000 shares; no shares issued and outstanding as of March 31, 2015 or December 31, 2014	0	0
Common stock	310,544	323,596
Retained earnings	599,727	587,862
Accumulated other comprehensive income, net	4,179	(2,534)
Total stockholders' equity	914,450	908,924
Total liabilities and stockholders' equity	$ 8,528,542	$ 8,609,936