CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - UNAUDITED - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Operating activities:
Net income	$ 15,089	$ 13,474	$ 44,942	$ 34,934
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			5,939	5,940
Provision for loan losses	934	781	2,450	4,974	$ 5,546
Share based compensation expense			1,611	1,341
Tax benefits associated with share based compensation			700	287
Deferred income tax expense			163	646
Origination of loans held for sale			(105,970)	(130,409)
Proceeds from sales of loans held for sale			114,474	151,077
Gains on sales of loans held for sale			(2,653)	(2,461)
(Gains) losses on sales of other real estate owned			(82)	48
Investment securities gains	0	0	(1,275)	(1,919)
Increase (Decrease) in Operating Capital [Abstract]
Net (increase) decrease in accrued interest receivable			(1,456)	320
Net decrease in other assets			(5,314)	(1,731)
Net increase (decrease) in accrued expenses and other liabilities			19	(5,999)
Other - net			3,521	(731)
Net cash provided by operating activities			57,069	56,317
Investing activities:
Proceeds of other equity securities			6,241	5,507
Purchases of investments available-for-sale			(125,028)	(120,273)
Proceeds from sales of investment available-for-sale			2,251	40,863
Proceeds from maturities, calls and principal payments of investments held-to-maturity			0	5,004
Proceeds from maturities, calls and principal payments of investments available-for-sale			103,775	227,419
Net increase in loans and leases			(306,755)	(303,709)
Proceeds from the sales of other real estate owned			1,228	1,393
Proceeds from sales of loans previously held for investment			40,031	0
Acquisition of business activity, net of cash acquired			0	(1,347)
Expenditures for premises and equipment			(4,589)	(4,250)
Net cash (used) in investing activities			(282,846)	(149,393)
Financing activities:
Net increase in deposits			378,248	273,427
Net increase in retail repurchase agreements and federal funds purchased			21,450	15,060
Proceeds from advances from FHLB			3,080,000	1,805,000
Repayment of advances from FHLB			(3,237,083)	(1,940,000)
Retirement of subordinated debt			(30,000)	(5,000)
Proceeds from issuance of common stock			1,015	1,268
Stock tendered for payment of withholding taxes			(953)	(683)
Repurchase of common stock			0	(13,273)
Dividends paid			(18,844)	(17,408)
Net cash provided by financing activities			193,833	118,391
Net increase (decrease) in cash and cash equivalents			(31,944)	25,315
Cash and cash equivalents at beginning of period			134,125	72,882	72,882
Cash and cash equivalents at end of period	$ 102,181	$ 98,197	102,181	98,197	$ 134,125
Supplemental Disclosures:
Interest payments			19,244	16,193
Income tax payments			22,927	16,825
Transfer of Investments Held-to-maturity to Available For Sale Securities			0	203,118
Transfer from loans to residential mortgage loans held for sale			39,744	18,752
Transfers from loans to other real estate owned			$ 700	$ 0