Quarterly Financial Summary (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]
Interest income	$ 77,794	$ 75,415	$ 72,151	$ 67,613	$ 66,556	$ 65,010	$ 62,334	$ 60,826	$ 292,973	$ 254,726	$ 216,578
Interest expense	13,120	12,318	11,162	9,899	8,831	8,881	8,020	7,723	46,499	33,455	22,833
Net interest income	64,674	63,097	60,989	57,714	57,725	56,129	54,314	53,103	246,474	221,271	193,745
Provision for loan losses	3,306	3,716	2,498	3,650	4,063	2,896	1,843	2,162	13,170	10,964	12,986
Net interest income after provision for loan losses	61,368	59,381	58,491	54,064	53,662	53,233	52,471	50,941	233,304	210,307	180,759
Noninterest income	38,186	41,901	34,987	47,467	32,435	32,441	31,676	28,092	162,541	124,644	105,061
Noninterest expenses	61,350	52,454	57,831	53,412	68,065	54,163	52,727	51,506	225,047	226,461	188,666
Income before taxes	38,204	48,828	35,647	48,119	18,032	31,511	31,420	27,527	170,798	108,490	97,154
Income tax provision	8,486	9,893	6,907	10,769	27,864	10,942	10,850	8,590	36,055	58,246	33,074
Net income	$ 29,718	$ 38,935	$ 28,740	$ 37,350	$ (9,832)	$ 20,569	$ 20,570	$ 18,937	$ 134,743	$ 50,244	$ 64,080
Earnings Per Share [Abstract]
Basic (in dollars per share)	$ 0.94	$ 1.22	$ 0.91	$ 1.19	$ (0.31)	$ 0.65	$ 0.65	$ 0.60	$ 4.27	$ 1.60	$ 2.12
Diluted (in dollars per share)	$ 0.93	$ 1.20	$ 0.89	$ 1.16	$ (0.31)	$ 0.64	$ 0.64	$ 0.59	$ 4.19	$ 1.56	$ 2.06