Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Operating Activities:
Net income	$ 37,817	$ 34,343	$ 95,058	$ 106,322
Adjustment to reconcile net income to net cash provided by operating activities:
Provision for credit losses		(3,000)	3,000	(13,000)	$ (13,000)
Depreciation and amortization			19,023	19,914
Amortization of intangibles	923	949	2,672	3,042
Amortization of debt securities premium and discount, net			7,751	9,461
Share-based compensation expense			6,856	5,749
Security gains, net	(1)	(33)	(89)	(88)
Net deferred loan origination expense			(5,059)	(5,073)
Excess tax benefit from exercise of stock options			(1,247)	(867)
Increase in interest receivable			(682)	386
Increase (decrease) in interest payable			1,036	(47)
Realized gain on mortgages sold			(40,209)	(34,965)
Proceeds from mortgages sold			1,249,605	1,134,164
Origination of mortgages held for sale			(1,256,131)	(1,130,433)
Loss on other real estate owned, net	(525)	(321)	2,254	2,956
Increase in bank-owned life insurance			(5,481)	(5,491)
Other, net			15,465	14,532
Net cash provided by (used in) operating activities			93,822	106,562
Investing activities:
Proceeds from calls and maturities of available-for-sale securities			315,221	276,707
Proceeds from sales of available-for-sale securities			15	1,110
Purchases of available-for-sale securities			(690,820)	(294,853)
Net increase in loans and leases			(293,761)	(503,869)
Purchases of premises and equipment			(17,637)	(20,125)
Proceeds from sale of premises and equipment			1,362	549
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			10,352	13,033
Other, net			(87)	(12)
Net cash provided by (used in) investing activities			(679,071)	(524,718)
Financing activities:
Net increase in deposits			258,898	169,607
Net decrease in short-term debt and other liabilities			1,023	258,024
Advances of long-term debt			500,000
Repayment of long-term debt			(6,280)	(6,280)
Issuance of common stock			1,879	6,071
Repurchase of common stock			(14,162)	(70,439)
Excess tax benefit from exercise of stock options			1,247	867
Payment of cash dividends			(30,599)	(23,953)
Net cash provided by financing activities			712,006	333,897
Increase in cash and cash equivalents			126,757	(84,259)
Cash and cash equivalents at beginning of period			197,969	357,250	357,250
Cash and cash equivalents at end of period	$ 324,726	$ 272,991	324,726	272,991	$ 197,969
Supplemental Cash Flow Information
Income tax payments, net			36,897	58,298
Interest paid			20,634	21,923
Transfers of loans to other real estate owned			9,266	5,868
MSR fair value adjustment			(10,233)	(4,026)
Financed sales of other real estate owned			$ 673	1,178
Transfers of loans held for sale to loan portfolio				$ 75