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