Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Operating Activities:
Net income	$ 34,692	$ 39,713	$ 57,241	$ 71,979
Adjustment to reconcile net income to net cash provided by operating activities:
Provision for credit losses	2,000	(5,000)	3,000	(10,000)	$ (13,000)
Depreciation and amortization			12,606	13,411
Amortization of intangibles	869	1,061	1,749	2,093
Amortization of debt securities premium and discount, net			5,200	6,503
Share-based compensation expense			4,679	3,904
Security gains, net	(86)	(41)	(88)	(55)
Net deferred loan origination expense			(3,335)	(3,295)
Excess tax benefit from exercise of stock options			(1,103)	(702)
Increase in interest receivable			1,256	920
Increase (decrease) in interest payable			656	94
Realized gain on mortgages sold			(23,516)	(21,672)
Proceeds from mortgages sold			745,752	687,076
Origination of mortgages held for sale			(777,951)	(728,269)
Loss on other real estate owned, net	(886)	(1,200)	1,729	2,634
Increase in bank-owned life insurance			(3,706)	(3,649)
Other, net			16,261	12,949
Net cash provided by (used in) operating activities			40,430	33,921
Investing activities:
Proceeds from calls and maturities of available-for-sale securities			224,051	151,206
Proceeds from sales of available-for-sale securities			15	1,110
Purchases of available-for-sale securities			(229,469)	(261,356)
Net increase in loans and leases			(210,262)	(290,005)
Purchases of premises and equipment			(11,772)	(12,818)
Proceeds from sale of premises and equipment			949	139
Purchase of bank-owned life insurance, net of proceeds from death benefits				2,742
Acquisition of Insurance Agency			(3,716)
Proceeds from sale of other real estate owned			6,219	11,468
Other, net			(50)	(12)
Net cash provided by (used in) investing activities			(224,035)	(397,526)
Financing activities:
Net increase in deposits			33,206	162,622
Net decrease in short-term debt and other liabilities			(51,997)	76,806
Advances of long-term debt			300,000
Repayment of long-term debt			(4,187)	(4,186)
Issuance of common stock			207	5,168
Repurchase of common stock			(971)	(2,288)
Excess tax benefit from exercise of stock options			1,103	702
Payment of cash dividends			(18,872)	(14,490)
Net cash provided by financing activities			258,489	224,334
Increase in cash and cash equivalents			74,884	(139,271)
Cash and cash equivalents at beginning of period			197,969	357,250	357,250
Cash and cash equivalents at end of period	$ 272,853	$ 217,979	$ 272,853	$ 217,979	$ 197,969