Summary of Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net Interest Income	$ 110,283	$ 110,678	$ 101,409	$ 91,584	$ 92,856	$ 89,844	$ 74,580	$ 73,028	$ 413,954	$ 330,308	$ 294,666
Provision for loan losses	9,681	5,238	4,831	4,263	5,328	5,705	889	3,641	24,013	15,563	11,694
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	100,602	105,440	96,578	87,321	87,528	84,139	73,691	69,387	389,941	314,745	282,972
Noninterest income	27,045	29,765	27,634	24,716	25,528	24,977	25,624	25,893	109,160	102,022	113,601
Noninterest expense	88,821	92,539	88,882	83,646	77,878	78,759	69,298	71,740	353,888	297,675	279,668
Income taxes	6,685	8,956	7,451	5,123	21,506	8,725	8,059	5,530	28,215	43,820	36,556
NET INCOME	32,141	33,710	27,879	23,268	13,672	21,632	21,958	18,010	116,998	75,272	80,349
Preferred dividends	0	(13)	(13)	(13)	(13)	(13)	(13)	(19)	(39)	(58)	(292)
Interest expense on convertible preferred debt					0	3	4	5	0	12	51
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 32,141	$ 33,697	$ 27,866	$ 23,255	$ 13,659	$ 21,622	$ 21,949	$ 17,996	$ 116,959	$ 75,226	$ 80,108
Per share:
Earnings per share — basic (in dollars per share)	$ 0.93	$ 0.98	$ 0.85	$ 0.76	$ 0.46	$ 0.73	$ 0.82	$ 0.68	$ 3.54	$ 2.67	$ 3.26
Earnings per share — diluted (in dollars per share)	0.93	0.97	0.85	0.76	0.45	0.72	0.81	0.68	3.52	2.65	3.22
Cash dividends declared on common stock (in dollars per share)	0.19	0.14	0.13	0.13	0.18	0.11	0.11	0.11	$ 0.59	$ 0.51	$ 0.50
Book value per common share (in dollars per share)	$ 38.44	$ 37.14	$ 36.44	$ 33.81	$ 33.07	$ 32.75	$ 30.15	$ 29.26
Weighted average common shares outstanding (in shares)	34,474,336	34,452,377	32,620,775	30,441,776	29,948,536	29,647,534	26,686,845	26,334,788	33,012,000	28,168,000	24,573,000
Weighted average diluted common shares outstanding (in shares)	34,670,180	34,644,187	32,830,751	30,645,212	30,209,043	29,910,437	26,972,580	26,627,830	33,213,000	28,426,000	24,873,000