Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating activities:
Net income	$ 13,579	$ 10,602	$ 26,983	$ 21,393
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	1,235	600	1,970	1,500	$ 2,550
Depreciation, amortization and accretion, net			2,680	4,399
Deferred income tax provision			40	(517)
Gain on sales of mortgage loans held for sale			(769)	(963)
Origination of mortgage loans held for sale			(37,803)	(49,168)
Proceeds from sale of mortgage loans held for sale			39,483	50,289
Bank owned life insurance income			(378)	(760)
Gain on the disposal of premises and equipment			(14)
(Gain) loss on the sale of other real estate			(109)	64
Stock compensation expense			2,035	1,342
Excess tax benefits from share-based compensation arrangements			(525)	(1,120)
Decrease (increase) in accrued interest receivable and other assets			2,077	(4,015)
(Decrease) increase in accrued interest payable and other liabilities			(2,136)	6,883
Net cash provided by operating activities			33,534	29,327
Investing activities:
Purchases of securities available for sale			(399,911)	(251,196)
Proceeds from maturities of securities available for sale			392,855	245,010
Purchases of Federal Home Loan Bank stock			(2,724)	(1,319)
Net increase in loans			(170,843)	(4,685)
Purchases of premises and equipment			(2,694)	(839)
Proceeds from disposal of premises and equipment			230	207
Proceeds from mortality benefit of bank owned life insurance				970
Proceeds from sale of foreclosed assets			2,860	1,784
Net cash used in investing activities			(180,227)	(10,068)
Financing activities:
Net decrease in deposits			(37,834)	(42,002)
Net increase in securities sold under agreements to repurchase and federal funds purchased			113,443	111,518
Proceeds from Federal Home Loan Bank advances			60,000	60,000
Repayments of Federal Home Loan Bank advances			(60,637)	(60,642)
Repurchase common stock for performance stock units			(155)	(216)
Common stock repurchases of restricted shares surrendered for taxes			(1,931)	(1,946)
Cash dividends paid			(10,441)	(8,819)
Net cash provided by financing activities			62,445	57,893
Net (decrease) increase in cash and cash equivalents			(84,248)	77,152
Cash and cash equivalents at beginning of period			139,248	47,973	47,973
Cash and cash equivalents at end of period	$ 55,000	$ 125,125	55,000	125,125	$ 139,248
Supplemental cash flow information:
Income tax payments			1,800	4,473
Cash paid for interest			5,497	3,187
Supplemental non-cash activity:
Transfers from loans to other real estate owned			$ 471