Condensed Consolidated Statements of Cash Flows $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Cash flows from operating activities:
Net income	$ 65,688	$ 40,661
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation	2,622	2,426
Provision for loan losses	4,524	7,223
Deferred income taxes	2,822	1,239
Net amortization of debt securities	1,338	2,064
Amortization of intangible assets	1,908	1,920
Gain on sale of investment securities	(9)	(22)
Mortgage loans originated for sale	(30,136)	(115,365)
Proceeds from mortgage loans sold	32,839	118,798
Gain on sale of other real estate	(13)	(17)
Gain on state tax credits, net	(508)	(332)
Share-based Compensation	2,554	2,514
Net accretion of loan discount	(1,253)	(3,796)
Changes in:
Accrued interest receivable	(5,811)	(302)
Accrued interest payable	703	249
Other assets	(16,309)	755
Other liabilities	(1,093)	(44,398)
Net cash provided by operating activities	59,866	13,617
Cash flows from investing activities:
Proceeds from Previous Acquisition	0	4,456
Net increase in loans	(172,449)	(201,715)
Proceeds from the sale of securities, available for sale	1,451	144,076
Proceeds from the paydown or maturity of securities, available for sale	61,881	126,073
Proceeds from the paydown or maturity of securities, held to maturity	4,988	4,145
Proceeds from the redemption of other investments	30,593	29,159
Proceeds from the sale of state tax credits held for sale	3,056	4,391
Proceeds from the sale of other real estate	467	2,513
Payments for the purchase/origination of:
Available for sale debt securities	(108,121)	(263,453)
Other investments	(44,597)	(45,224)
State tax credits held for sale	(4,704)	(145)
Fixed assets, net	(2,369)	(1,864)
Net cash used in investing activities	(229,804)	(197,588)
Cash flows from financing activities:
Net (decrease) increase in noninterest-bearing deposit accounts	(61,781)	20,684
Net increase in interest-bearing deposit accounts	115,843	39,998
Proceeds from Federal Home Loan Bank advances	1,142,500	1,394,181
Repayments of Federal Home Loan Bank advances	(914,000)	(1,145,681)
Proceeds from Issuance of Long-term Debt	0	10,000
Net decrease in other borrowings	(91,879)	(123,987)
Cash dividends paid on common stock	(7,866)	(7,709)
Payments for Repurchase of Common Stock	6,840	16,636
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures	(3,297)	(2,573)
Net cash provided by financing activities	172,680	168,277
Net increase (decrease) in cash and cash equivalents	2,742	(15,694)
Cash and cash equivalents, beginning of period	153,323	198,802
Cash and cash equivalents, end of period	156,065	183,108
Supplemental Cash Flow Information [Abstract]
Cash paid during the period for interest	31,785	16,948
Cash paid during the period for income taxes	8,492	9,382
Noncash transactions:
Transfer to other real estate owned in settlement of loans	$ 0	$ 289
Common shares issued related to acquisition	0	141,729