Parent Company - Only Financial Statements - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash	$ 48,456	$ 60,024	$ 50,765	$ 143,067
Premises and equipment, net	65,648	54,458
Goodwill	184,012	179,889	104,765
Other assets	61,277	46,185
Total assets	4,652,485	4,449,720	3,421,500
Liabilities and shareholders’ equity:
Subordinated notes	98,526	98,416
Junior subordinated debentures	21,580	21,416
Other liabilities	54,195	47,439
Total liabilities	4,087,781	3,921,601
Common stock, par value $1; authorized 100,000,000 shares; issued 24,545,348 and 24,360,049 shares as of December 31, 2018 and December 31, 2017, respectively, and outstanding of 20,163,816 and 20,161,395 as of December 31, 2018 and December 31, 2017, respectively	24,545	24,360
Paid-in capital in excess of par value	374,010	371,486
Less: Common stock in treasury at cost - 4,381,532 and 4,198,654 shares as of December 31, 2018 and December 31, 2017, respectively	(75,883)	(68,179)
Accumulated other comprehensive loss, net of tax	(7,513)	(4,414)
Retained earnings	250,230	205,549
Total shareholders’ equity	565,389	528,802
Total liabilities and shareholders’ equity	4,652,485	4,449,720
Parent Company
Assets
Cash	78,143	68,535	$ 23,663	$ 37,992
Investment securities	418	458
Investments in subsidiaries, as equity in net assets	606,023	580,230
Premises and equipment, net	2,091	2,189
Goodwill	245	245
Other assets	1,060	1,135
Total assets	687,980	652,792
Liabilities and shareholders’ equity:
Subordinated notes	98,526	98,416
Junior subordinated debentures	21,580	21,416
Other liabilities	2,485	4,158
Total liabilities	122,591	123,990
Common stock, par value $1; authorized 100,000,000 shares; issued 24,545,348 and 24,360,049 shares as of December 31, 2018 and December 31, 2017, respectively, and outstanding of 20,163,816 and 20,161,395 as of December 31, 2018 and December 31, 2017, respectively	24,545	24,360
Paid-in capital in excess of par value	374,010	371,486
Less: Common stock in treasury at cost - 4,381,532 and 4,198,654 shares as of December 31, 2018 and December 31, 2017, respectively	(75,883)	(68,179)
Accumulated other comprehensive loss, net of tax	(7,513)	(4,414)
Retained earnings	250,230	205,549
Total shareholders’ equity	565,389	528,802
Total liabilities and shareholders’ equity	$ 687,980	$ 652,792