Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 39,796	$ 38,766	$ 39,135
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provision for loan losses	4,275	8,231	4,351
Depreciation and amortization of premises and equipment	4,412	4,952	5,041
Amortization of FDIC indemnification asset, net	1,159	1,321	891
Accretion of purchase discounts or premiums, net	(2,814)	(676)	(230)
Other amortization	1,321	1,411	481
Impairment of other real estate	1,058	1,090	460
Amortization and impairment of servicing rights, net	19,806	19,527	15,885
Share-based compensation expense	4,624	3,544	1,468
Postretirement benefits, net	2,018	15	1,820
Net (gain) loss on investment securities called or sold	0	(578)	329
Gains on loan sales, including origination of servicing rights	(86,941)	(97,525)	(84,635)
Net gain on sales of other real estate	(659)	(859)	(3,084)
Loss on disposal of premises and equipment	0	0	140
Net income on bank owned life insurance	(1,732)	(1,853)	(2,400)
Net change in deferred income tax, net of acquisitions	2,233	8,010	6,540
Net change in fair value of loans held-for-sale	(1,426)	86	(2,490)
Originations of loans held-for-sale	(2,960,006)	(3,455,029)	(3,216,100)
Proceeds from sales of loans held-for-sale	3,122,820	3,452,655	3,232,045
Net payments received from (paid to) FDIC under loss-share agreements	487	(92)	480
Increase (decrease) in other assets, net of acquisitions	4,611	(1,969)	(464)
Increase (decrease) in other liabilities, net of acquisitions	159	(10,535)	3,292
Net cash provided by (used in) operating activities	155,201	(29,508)	2,955
Cash flows from investing activities:
Purchases of investment securities available-for-sale	0	(12,391)	(30,821)
Proceeds from sales of investment securities available-for-sale	0	0	22,633
Maturities, calls and repayment of investment securities available-for-sale	22,536	41,668	27,799
Purchases of investment securities held-to-maturity	(7,000)	(3,929)	(5,018)
Maturities, calls and repayment of investment securities held-to-maturity	1,798	1,661	1,163
Purchases of FHLB stock	(11,993)	(14,008)	(10,195)
Redemption of FHLB stock	15,937	11,050	11,487
Net increase in loans, net of loans acquired	(282,213)	(270,119)	(463,366)
Proceeds from bank owned life insurance	0	847	844
Purchase of bank owned life insurance	0	(2,500)	(5,000)
Proceeds from sales of other real estate	8,921	11,561	17,682
Purchases of premises and equipment, net of acquisitions	(5,305)	(6,529)	(12,160)
Cash received in excess of cash paid for acquisitions	0	37,609	215,472
Net cash used in investing activities	(257,319)	(205,080)	(229,480)
Cash flows from financing activities:
Net increase in noninterest-bearing deposits, net of acquisitions	160,698	113,756	138,794
Net increase in interest-bearing deposits, net of acquisitions	75,908	153,644	127,032
Net increase (decrease) in other short-term borrowings	7,229	(26,379)	(65,626)
Proceeds from FHLB advances	475,000	1,325,000	910,000
Repayments of FHLB advances	(575,000)	(1,265,000)	(940,000)
Issuance of subordinated debt	0	0	75,000
Payment of debt issuance costs	0	0	(1,069)
Repurchase of common stock	(1,673)	(821)	(796)
Proceeds from the issuance of common stock, net	9,295	10,153	6,348
Cash dividends paid on common stock	(12,748)	(12,187)	(8,630)
Net cash provided by financing activities	138,709	298,166	241,053
Net increase in cash and cash equivalents	36,591	63,578	14,528
Cash and cash equivalents, beginning of year	149,711	86,133	71,605
Cash and cash equivalents, end of year	186,302	149,711	86,133
Cash paid during the year for:
Interest on deposits and borrowings	22,335	20,031	15,099
Income taxes	10,888	17,895	9,518
Acquisitions:
Assets acquired	0	167,366	255,280
Liabilities assumed	0	186,030	470,752
Common stock issued	0	22,727	0
Transfers of investment securities from available-for-sale to held-to-maturity	0	0	3,194
Transfers from loans held-for-sale to loans held for investment	5,905	4,573	6,349
Transfers of loans to other real estate	$ 2,127	$ 7,120	$ 4,742