Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Proceeds from sale of loan production office	$ 932	$ 0
Cash flows from operating activities:
Net income	45,678	43,202
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	6,550	2,435
Net (gain) loss on disposal of property and equipment	188	(856)
Depreciation and amortization	9,491	9,090
Net premium amortization on investment securities	6,347	7,021
Net gains on investment securities transactions	(87)	(52)
Net gains on sales of mortgage loans held for sale	(10,544)	(10,759)
Net gain on sale of OREO	(636)	(1,736)
Write-downs of OREO and other assets pending disposal	621	106
Net reversal of impairment of mortgage servicing rights	(5)	(71)
Deferred income tax expense	321	9,108
Net increase in cash surrender value of company-owned life insurance policies	(2,271)	(1,304)
Stock-based compensation expense	2,385	2,319
Tax benefits from stock-based compensation expense	619	804
Excess tax benefits from stock-based compensation	(495)	(530)
Originations of loans held for sale	(468,560)	(561,779)
Proceeds from sales of loans held for sale	457,132	546,871
Changes in operating assets and liabilities:
Increase in interest receivable	281	(1,945)
Increase in other assets	(14,551)	(1,034)
Decrease in accrued interest payable	687	(467)
Decrease in accounts payable and accrued expenses	3,701	(12,268)
Net cash provided by operating activities	36,852	28,155
Cash flows from investing activities:
Purchases of held-to-maturity investment securities	(9,883)	(27,640)
Purchases of available-for-sale investment securities	(459,569)	(223,483)
Proceeds from maturities and paydowns of held-to-maturity investment securities	53,977	55,654
Proceeds from maturities and paydowns of available-for-sale investment securities	424,458	337,538
Purchases of company-owned life insurance	0	22,500
Extensions of credit to customers, net of repayments	(159,410)	(190,392)
Recoveries of loans charged-off	4,717	3,285
Proceeds from sales of OREO	2,398	7,807
Capital expenditures, net of sales	(3,638)	514
Net cash used in investing activities	(146,018)	(59,217)
Cash flows from financing activities:
Net increase (decrease) in deposits	(107,489)	(201,811)
Net increase (decrease) in repurchase agreements	(44,236)	(33,105)
Net increase (decrease) in other borrowed funds	13	(6)
Repayments of long-term debt	(32)	(30)
Advances on long-term debt	75	5,031
Proceeds from issuance of common stock	1,684	1,670
Excess tax benefits from stock-based compensation	495	530
Purchase and retirement of common stock	(26,042)	(15,264)
Dividends paid to common stockholders	(19,708)	(18,189)
Net cash provided by (used in) financing activities	(195,240)	(261,174)
Net increase (decrease) in cash and cash equivalents	(304,406)	(292,236)
Cash and cash equivalents at beginning of period	780,457	798,670
Cash and cash equivalents at end of period	476,051	506,434
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	27,566	18,450
Cash paid during the period for interest expense	8,069	9,364
Transfer of loans to other real estate owned	4,019	4,396
Capitalization of internally originated mortgage servicing rights	$ 1,768	$ 1,792