Condensed Financial Information (parent company only) - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Investment securities	$ 696,862	$ 658,400
Premises and equipment	94,432	97,648
Interest receivable	26,194	24,415
Goodwill	244,000	243,129	$ 202,724
Cash surrender value of life insurance	201,671	200,539
Tax asset, deferred and receivable	39,384	46,977
Other assets	30,706	24,023
TOTAL ASSETS	7,211,611	6,761,003
Liabilities
Subordinated debentures and term loans	128,445	127,846
Interest payable	3,110	3,092
Other liabilities	56,149	49,211
Total Liabilities	6,309,954	5,910,494
Stockholders' equity	901,657	850,509	$ 726,827	$ 634,923
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	7,211,611	6,761,003
Parent
Assets
Cash	31,944	43,622
Investment in subsidiaries	978,291	932,372
Investment securities	18,765
Premises and equipment	1,260	1,361
Interest receivable	47	47
Goodwill	448	448
Cash surrender value of life insurance	1,082	1,041
Tax asset, deferred and receivable	521	2,024
Other assets	5,274	5,195
TOTAL ASSETS	1,037,632	986,110
Liabilities
Subordinated debentures and term loans	127,427	127,663
Interest payable	880	873
Other liabilities	7,668	7,065
Total Liabilities	135,975	135,601
Stockholders' equity	901,657	850,509
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,037,632	$ 986,110