Summary of Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net interest income	$ 112,745	$ 111,321	$ 106,708	$ 102,955	$ 110,283	$ 110,678	$ 101,409	$ 91,584	$ 433,729	$ 413,954	$ 330,308
Provision for loan losses	4,903	5,201	4,918	1,635	9,681	5,238	4,831	4,263	16,657	24,013	15,563
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	107,842	106,120	101,790	101,320	100,602	105,440	96,578	87,321	417,072	389,941	314,745
Noninterest income	28,030	29,400	32,061	26,717	27,045	29,765	27,634	24,716	116,208	109,160	102,022
Noninterest expense	92,866	92,967	75,098	88,230	88,821	92,539	88,882	83,646	349,161	353,888	297,675
Income taxes	5,155	7,941	13,584	8,310	6,685	8,956	7,451	5,123	34,990	28,215	43,820
NET INCOME	37,851	34,612	45,169	31,497	32,141	33,710	27,879	23,268	149,129	116,998	75,272
Preferred dividends					0	(13)	(13)	(13)	0	(39)	(58)
Interest expense on convertible preferred debt									0	0	12
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 37,851	$ 34,612	$ 45,169	$ 31,497	$ 32,141	$ 33,697	$ 27,866	$ 23,255	$ 149,129	$ 116,959	$ 75,226
Per share:
Earnings per share — basic (in dollars per share)	$ 1.03	$ 0.94	$ 1.26	$ 0.91	$ 0.93	$ 0.98	$ 0.85	$ 0.76	$ 4.14	$ 3.54	$ 2.67
Earnings per share — diluted (in dollars per share)	1.03	0.94	1.26	0.91	0.93	0.97	0.85	0.76	4.14	3.52	2.65
Cash dividends declared on common stock (in dollars per share)	0.18	0.18	0.16	0.16	0.19	0.14	0.13	0.13	$ 0.68	$ 0.59	$ 0.51
Book value per common share (in dollars per share)	$ 43.00	$ 42.62	$ 41.48	$ 39.65	$ 38.44	$ 37.14	$ 36.44	$ 33.81
Weighted average common shares outstanding (in shares)	36,758,025	36,692,381	35,743,986	34,564,378	34,474,336	34,452,377	32,620,775	30,441,776	35,991,000	33,012,000	28,168,000
Weighted average diluted common shares outstanding (in shares)	36,840,519	36,835,191	35,879,259	34,699,839	34,670,180	34,644,187	32,830,751	30,645,212	36,062,000	33,213,000	28,426,000