Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 95,636	$ 86,795	$ 84,401
Adjustments to reconcile net income from operations to net cash provided by operating activities:
Provision for loan losses	(9,991)	(6,822)	6,622
Net (gain) loss on disposal of property and equipment	621	(731)	(1,256)
Depreciation and amortization	19,480	18,313	16,855
Net premium amortization on investment securities	12,520	14,880	14,690
Net gain on investment securities transactions	(330)	(137)	(61)
Net gain on sale of mortgage loans held for sale	(26,806)	(21,748)	(17,475)
Net gain on sale of OREO	(925)	(2,991)	(1,849)
Write-down of OREO and other assets pending disposal	792	1,013	326
Mortgage servicing rights impairment recovery	(35)	(97)	(136)
Deferred income tax expense	3,369	12,449	5,345
Net increase in cash surrender value of company-owned life insurance policies	(4,477)	(3,432)	(3,600)
Stock-based compensation expense	4,376	3,959	3,634
Tax benefits from stock-based compensation	2,146	1,443	2,193
Excess tax benefits from stock-based compensation	(1,566)	(1,184)	(2,205)
Originations of loans held for sale	(1,113,292)	(1,148,098)	(903,373)
Proceeds from Sale of Mortgage Loans Held-for-sale	1,125,365	1,164,804	923,350
Changes in operating assets and liabilities:
Decrease (increase) in accrued interest receivable	(1,053)	(101)	470
Increase in other assets	(2,214)	(3,622)	(6,956)
Increase (decrease) in accrued interest payable	445	(1,006)	286
Increase (decrease) in accounts payable and accrued expenses	(5,973)	(11,931)	13,991
Net cash provided by operating activities	118,070	115,400	122,008
Purchases of investment securities:
Held-to-maturity	(18,173)	(45,179)	(21,627)
Available-for-sale	(905,940)	(474,846)	(664,821)
Proceeds from maturities, paydowns, calls and sales of investment securities:
Held-to-maturity	112,563	118,406	47,784
Available-for-sale	814,598	648,683	613,930
Payments to Acquire Life Insurance Policies	0	(30,000)	(15,000)
Proceeds from sales of mortgage servicing rights	0	0	266
Extensions of credit to customers, net of repayments	(168,321)	(327,878)	(216,730)
Recoveries of loans charged-off	9,249	7,432	9,478
Proceeds from sales of OREO	5,325	15,644	12,381
Payments to Acquire Businesses, Net of Cash Acquired	18,554	(1,636)	35,556
Proceeds from Sales of Business, Affiliate and Productive Assets	932	0	0
Capital expenditures, net of proceeds from sales	(11,879)	(5,965)	2,941
Net cash used in investing activities	(143,092)	(95,339)	(195,842)
Cash flows from financing activities:
Net increase in deposits	77,586	19,160	357,083
Net increase in repurchase agreements	8,871	6,385	43,892
Net increase (decrease) in short-term borrowings	4	(7)	(12,720)
Proceeds from Issuance of Unsecured Debt	150	5,103	68
Repayments of long-term debt	(65)	(16,538)	(48)
Write off of Deferred Debt Issuance Cost	0	7	0
Repayment of junior subordinated debentures held by subsidiary trusts	0	0	(20,439)
Proceeds from issuance of common stock	4,683	3,369	6,299
Payments of Stock Issuance Costs	0	0	298
Excess tax benefits from stock-based compensation	1,566	1,184	2,205
Purchase and retirement of common stock	(26,854)	(20,647)	(9,739)
Dividends paid to common stockholders	(39,353)	(36,290)	(28,626)
Net cash used in financing activities	26,588	(38,274)	337,677
Net increase (decrease) in cash and cash equivalents	1,566	(18,213)	263,843
Cash and cash equivalents at beginning of year	780,457	798,670	534,827
Cash and cash equivalents at end of year	782,023	780,457	798,670
Supplemental disclosures of cash flow information:
Cash paid during the year for income taxes	54,419	27,335	26,650
Cash paid during the year for interest expense	$ 17,200	$ 18,933	$ 17,736