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	$ 11,704	$ 10,467	$ 33,097	$ 30,411
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	150	1,250	1,650	2,500	$ 3,000
Depreciation, amortization and accretion, net			6,848	8,016
Deferred income tax provision			(1,811)	(320)
Gain on call of securities available for sale	(31)		(31)
Gain on sales of mortgage loans held for sale			(1,453)	(1,825)
Origination of mortgage loans held for sale			(74,857)	(91,195)
Proceeds from sale of mortgage loans held for sale			74,064	93,861
Bank owned life insurance income	(204)	(216)	(964)	(657)
Loss on the disposal of premises and equipment				163
(Gain) on the sale of foreclosed assets			(39)	(382)
Stock compensation expense			2,012	1,646
Excess tax benefits from share-based compensation arrangements			(1,353)	(963)
Decrease in accrued interest receivable and other assets			(5,651)	(6,145)
Increase in accrued interest payable and other liabilities			18,062	14,253
Net cash provided by operating activities			49,574	49,363
Investing activities:
Purchases of securities available for sale			(422,190)	(327,711)
Proceeds from sale of securities available for sale
Proceeds from maturities of securities available for sale			420,179	355,943
Purchase of Federal Home Loan Bank stock			(1,319)
Net increase in loans			(30,454)	(191,793)
Purchases of premises and equipment			(1,733)	(5,853)
Proceeds from mortality benefit of bank owned life insurance			970
Proceeds from sale of foreclosed assets			2,432	1,403
Net cash used in investing activities			(32,115)	(168,011)
Financing activities:
Net (decrease) increase in deposits			(38,582)	18,895
Net increase in securities sold under agreements to repurchase and federal funds purchased			118,855	56,699
Proceeds from Federal Home Loan Bank advances			90,000	199,000
Repayments of Federal Home Loan Bank advances			(90,965)	(191,102)
Proceeds (used for) and received from settlement of stock awards			(216)	1,599
Excess tax benefits from share-based compensation arrangements				963
Common stock repurchases			(2,113)	(1,534)
Cash dividends paid			(13,333)	(11,812)
Net cash provided by financing activities			63,646	72,708
Net increase (decrease) in cash and cash equivalents			81,105	(45,940)
Cash and cash equivalents at beginning of period			47,973	103,833	103,833
Cash and cash equivalents at end of period	$ 129,078	$ 57,893	129,078	57,893	$ 47,973
Supplemental cash flow information:
Income tax payments			11,063	9,190
Cash paid for interest			5,109	3,636
Supplemental non-cash activity:
Transfers from loans to foreclosed assets				$ 1,522