Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 63,364	$ 61,625
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	3,533	(6,740)
Net (gain) loss on disposal of property and equipment	(822)	(68)
Depreciation and amortization	13,702	12,168
Net premium amortization on investment securities	11,527	10,784
Net gains on investment securities transactions	(75)	(80)
Net gains on sales of mortgage loans held for sale	(16,397)	(12,947)
Net gain on sale of OREO	(2,862)	(551)
Write-downs of OREO and other assets pending disposal	985	87
Net reversal of impairment of mortgage servicing rights	(147)	(117)
Deferred income tax expense	12,975	8,537
Net increase in cash surrender value of company-owned life insurance policies	(9,669)	(2,540)
Stock-based compensation expense	3,231	2,906
Tax benefits from stock-based compensation expense	979	1,541
Excess tax benefits from stock-based compensation	(884)	(1,503)
Originations of loans held for sale	(856,384)	(682,011)
Proceeds from sales of loans held for sale	865,833	676,061
Changes in operating assets and liabilities:
Increase in interest receivable	(3,962)	(2,749)
Increase in other assets	(4,766)	(1,585)
Decrease in accrued interest payable	(639)	22
Decrease in accounts payable and accrued expenses	(17,583)	1,321
Net cash provided by operating activities	61,939	64,161
Cash flows from investing activities:
Purchases of held-to-maturity investment securities	(28,745)	(10,431)
Purchases of available-for-sale investment securities	(253,049)	(322,838)
Proceeds from maturities and paydowns of held-to-maturity investment securities	80,759	29,432
Proceeds from maturities and paydowns of available-for-sale investment securities	450,462	398,383
Purchases of company-owned life insurance	(22,500)	(15,000)
Proceeds from sales of mortgage servicing rights	0	266
Extensions of credit to customers, net of repayments	(251,450)	(148,854)
Recoveries of loans charged-off	4,439	7,323
Proceeds from sales of OREO	13,586	5,877
Acquisition of bank and bank holding company, net of cash and cash equivalents received	1,636	(35,556)
Capital expenditures, net of sales	(2,236)	(6,599)
Net cash used in investing activities	(10,370)	(26,885)
Cash flows from financing activities:
Net increase (decrease) in deposits	(33,983)	310,370
Net increase (decrease) in repurchase agreements	(66,717)	(25,880)
Net increase (decrease) in other borrowed funds	1	(11,926)
Repayments of long-term debt	(1,297)	(35)
Advances on long-term debt	5,066	0
Proceeds from issuance of common stock	1,909	4,914
Excess tax benefits from stock-based compensation	884	1,503
Purchase and retirement of common stock	(20,548)	(9,736)
Dividends paid to common stockholders	(27,259)	(21,350)
Net cash provided by (used in) financing activities	(141,944)	247,860
Net increase (decrease) in cash and cash equivalents	(90,375)	285,136
Cash and cash equivalents at beginning of period	798,670	534,827
Cash and cash equivalents at end of period	708,295	819,963
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	27,335	21,100
Cash paid during the period for interest expense	$ 13,853	$ 13,049