Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 70,871	$ 63,364
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	8,913	3,533
Net (gain) loss on disposal of property and equipment	492	(822)
Depreciation and amortization	14,482	13,702
Net premium amortization on investment securities	9,423	11,527
Net gains on investment securities transactions	(312)	(75)
Net gains on sales of mortgage loans held for sale	(15,126)	(16,397)
Net gain on sale of OREO	(693)	(2,862)
Write-downs of OREO and other assets pending disposal	621	985
Net reversal of impairment of mortgage servicing rights	(21)	(147)
Deferred income tax expense	(344)	12,975
Net increase in cash surrender value of company-owned life insurance policies	(3,431)	(2,169)
Stock-based compensation expense	3,350	3,231
Tax benefits from stock-based compensation expense	1,352	979
Excess tax benefits from stock-based compensation	(1,126)	(884)
Originations of loans held for sale	(799,445)	(856,384)
Proceeds from sales of loans held for sale	795,527	865,833
Changes in operating assets and liabilities:
Increase in interest receivable	(2,203)	(3,962)
Increase in other assets	(2,644)	(4,766)
Decrease in accrued interest payable	646	(639)
Decrease in accounts payable and accrued expenses	(1,278)	(17,583)
Net cash provided by operating activities	79,054	69,439
Cash flows from investing activities:
Purchases of held-to-maturity investment securities	(18,170)	(28,745)
Purchases of available-for-sale investment securities	(626,574)	(253,049)
Proceeds from maturities and paydowns of held-to-maturity investment securities	86,306	80,759
Proceeds from maturities and paydowns of available-for-sale investment securities	652,064	450,462
Purchases of company-owned life insurance	0	30,000
Extensions of credit to customers, net of repayments	(203,216)	(251,450)
Recoveries of loans charged-off	6,363	4,439
Proceeds from sales of OREO	3,352	13,586
Acquisition of banks and bank holding companies, net of cash and cash equivalents received	(18,554)	1,636
Proceeds from sale of loan production office	932	0
Capital expenditures, net of sales	(5,113)	(2,236)
Net cash used in investing activities	(85,502)	(17,870)
Cash flows from financing activities:
Net increase (decrease) in deposits	30,057	(33,983)
Net increase (decrease) in repurchase agreements	(51,917)	(66,717)
Net increase (decrease) in other borrowed funds	6	1
Repayments of long-term debt	(49)	(1,297)
Advances on long-term debt	113	5,066
Proceeds from issuance of common stock	3,657	1,909
Excess tax benefits from stock-based compensation	1,126	884
Purchase and retirement of common stock	(26,119)	(20,548)
Dividends paid to common stockholders	(29,516)	(27,259)
Net cash provided by (used in) financing activities	(72,642)	(141,944)
Net increase (decrease) in cash and cash equivalents	(79,090)	(90,375)
Cash and cash equivalents at beginning of period	780,457	798,670
Cash and cash equivalents at end of period	701,367	708,295
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	40,416	27,335
Cash paid during the period for interest expense	12,448	13,853
Transfer of loans to loans held for sale	50	10,619
Transfer of loans to other real estate owned	5,335	5,380
Capitalization of internally originated mortgage servicing rights	3,890	2,709
Transfer of bank buildings and land pending disposal to other assets	$ 0	$ 1,805