Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 84,401	$ 86,136	$ 58,224
Adjustments to reconcile net income from operations to net cash provided by operating activities:
Provision for loan losses	6,622	6,125	(40,750)
Net gain on disposal of property and equipment	(1,256)	(217)	(424)
Depreciation and amortization	16,855	16,245	17,112
Net premium amortization on investment securities	14,690	14,655	11,700
Net gain on investment securities transactions	(61)	(1)	(348)
Net gain on sale of mortgage loans held for sale	(17,475)	(24,482)	(29,606)
Net gain on sale of OREO	(1,849)	(3,232)	(1,041)
Write-down of OREO and other assets pending disposal	326	3,512	6,724
Mortgage servicing rights impairment recovery	(136)	(99)	(771)
Deferred income tax expense	5,345	11,276	8,762
Net increase in cash surrender value of company-owned life insurance policies	(3,600)	(446)	(1,849)
Stock-based compensation expense	3,014	2,936	2,485
Tax benefits from stock-based compensation	2,193	1,898	360
Excess tax benefits from stock-based compensation	(2,205)	(2,031)	(273)
Originations of loans held for sale	(903,373)	(1,557,288)	(1,197,744)
Proceeds from Sale of Mortgage Loans Held-for-sale	923,350	1,603,770	1,209,866
Changes in operating assets and liabilities:
Decrease in accrued interest receivable	470	2,419	3,105
Decrease (increase) in other assets	(6,956)	3,440	4,498
Increase (decrease) in accrued interest payable	286	(1,539)	(1,621)
Increase (decrease) in accounts payable and accrued expenses	13,991	(602)	5,913
Net cash provided by operating activities	121,388	150,225	135,822
Purchases of investment securities:
Held-to-maturity	(21,627)	(16,370)	(68,305)
Available-for-sale	(664,821)	(741,579)	(1,246,068)
Proceeds from maturities, paydowns, calls and sales of investment securities:
Held-to-maturity	47,784	19,465	12,192
Available-for-sale	613,930	722,447	1,252,266
Payments to Acquire Life Insurance Policies	(15,000)	(45,000)	0
Proceeds from sales of mortgage servicing rights	266	470	907
Extensions of credit to customers, net of repayments	(216,730)	(178,580)	(128,919)
Recoveries of loans charged-off	9,478	11,466	8,116
Proceeds from sales of OREO	12,381	28,397	42,814
Capital contribution to equity method investment	0	0	(900)
Capital distribution from unconsolidated subsidiary	0	0	1,238
Payments to Acquire Businesses, Net of Cash Acquired	35,556	0	0
Capital expenditures, net of proceeds from sales	2,941	(5,653)	(14,420)
Net cash used in investing activities	(195,842)	(204,937)	(141,079)
Cash flows from financing activities:
Net increase (decrease) in deposits	357,083	(106,661)	413,440
Net increase (decrease) in repurchase agreements	43,892	(48,348)	(10,458)
Net increase (decrease) in short-term borrowings	(12,720)	(29)	25
Proceeds from Issuance of Unsecured Debt	68	0	0
Repayments of long-term debt	(48)	(243)	(40)
Payments for Repurchase of Preferred Stock and Preference Stock	0	(50,000)	0
Repayment of junior subordinated debentures held by subsidiary trusts	(20,439)	0	(41,238)
Proceeds from issuance of common stock	6,919	9,814	1,911
Payments of Stock Issuance Costs	298	0	0
Excess tax benefits from stock-based compensation	2,205	2,031	273
Purchase and retirement of common stock	(9,739)	(448)	(263)
Dividends paid to common stockholders	(28,626)	(17,909)	(26,208)
Dividends paid to preferred stockholders	0	0	(3,300)
Net cash used in financing activities	338,297	(211,793)	334,142
Net increase (decrease) in cash and cash equivalents	263,843	(266,505)	328,885
Cash and cash equivalents at beginning of year	534,827	801,332	472,447
Cash and cash equivalents at end of year	798,670	534,827	801,332
Supplemental disclosures of cash flow information:
Cash paid during the year for income taxes	26,650	39,879	17,540
Cash paid during the year for interest expense	$ 17,736	$ 22,234	$ 31,735