Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 86,795	$ 84,401	$ 86,136
Adjustments to reconcile net income from operations to net cash provided by operating activities:
Provision for loan losses	(6,822)	6,622	6,125
Net gain on disposal of property and equipment	(731)	(1,256)	(217)
Depreciation and amortization	18,313	16,855	16,245
Net premium amortization on investment securities	14,880	14,690	14,655
Net gain on investment securities transactions	(137)	(61)	(1)
Net gain on sale of mortgage loans held for sale	(21,748)	(17,475)	(24,482)
Net gain on sale of OREO	(2,991)	(1,849)	(3,232)
Write-down of OREO and other assets pending disposal	1,013	326	3,512
Mortgage servicing rights impairment recovery	(97)	(136)	(99)
Deferred income tax expense	12,449	5,345	11,276
Net increase in cash surrender value of company-owned life insurance policies	(3,432)	(3,600)	(446)
Stock-based compensation expense	3,959	3,634	2,936
Tax benefits from stock-based compensation	1,443	2,193	1,898
Excess tax benefits from stock-based compensation	(1,184)	(2,205)	(2,031)
Originations of loans held for sale	(1,148,098)	(903,373)	(1,557,288)
Proceeds from Sale of Mortgage Loans Held-for-sale	1,164,804	923,350	1,603,770
Changes in operating assets and liabilities:
Decrease (increase) in accrued interest receivable	(101)	470	2,419
Decrease (increase) in other assets	(3,622)	(6,956)	3,440
Increase (decrease) in accrued interest payable	(1,006)	286	(1,539)
Increase (decrease) in accounts payable and accrued expenses	(11,931)	13,991	(602)
Net cash provided by operating activities	115,400	122,008	150,225
Purchases of investment securities:
Held-to-maturity	(45,179)	(21,627)	(16,370)
Available-for-sale	(474,846)	(664,821)	(741,579)
Proceeds from maturities, paydowns, calls and sales of investment securities:
Held-to-maturity	118,406	47,784	19,465
Available-for-sale	648,683	613,930	722,447
Payments to Acquire Life Insurance Policies	(30,000)	(15,000)	(45,000)
Proceeds from sales of mortgage servicing rights	0	266	470
Extensions of credit to customers, net of repayments	(327,878)	(216,730)	(178,580)
Recoveries of loans charged-off	7,432	9,478	11,466
Proceeds from sales of OREO	15,644	12,381	28,397
Payments to Acquire Businesses, Net of Cash Acquired	(1,636)	35,556	0
Capital expenditures, net of proceeds from sales	(5,965)	2,941	(5,653)
Net cash used in investing activities	(95,339)	(195,842)	(204,937)
Cash flows from financing activities:
Net increase (decrease) in deposits	19,160	357,083	(106,661)
Net increase (decrease) in repurchase agreements	6,385	43,892	(48,348)
Net decrease in short-term borrowings	(7)	(12,720)	(29)
Proceeds from Issuance of Unsecured Debt	5,103	68	0
Repayments of long-term debt	(16,538)	(48)	(243)
Write off of Deferred Debt Issuance Cost	7	0	0
Payments for Repurchase of Preferred Stock and Preference Stock	0	0	(50,000)
Repayment of junior subordinated debentures held by subsidiary trusts	0	(20,439)	0
Proceeds from issuance of common stock	3,369	6,299	9,814
Payments of Stock Issuance Costs	0	298	0
Excess tax benefits from stock-based compensation	1,184	2,205	2,031
Purchase and retirement of common stock	(20,647)	(9,739)	(448)
Dividends paid to common stockholders	(36,290)	(28,626)	(17,909)
Net cash used in financing activities	(38,274)	337,677	(211,793)
Net increase (decrease) in cash and cash equivalents	(18,213)	263,843	(266,505)
Cash and cash equivalents at beginning of year	798,670	534,827	801,332
Cash and cash equivalents at end of year	780,457	798,670	534,827
Supplemental disclosures of cash flow information:
Cash paid during the year for income taxes	27,335	26,650	39,879
Cash paid during the year for interest expense	$ 18,933	$ 17,736	$ 22,234