Quarterly Results of Operations (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]
Interest income	$ 129,846	$ 132,604	$ 132,414	$ 131,243	$ 136,021	$ 128,876	$ 92,699	$ 90,827	$ 526,107	$ 448,423	$ 270,005
Interest expense	16,927	20,269	21,773	19,837	18,475	16,163	11,528	9,546	78,806	55,712	22,503
Provision for credit losses	2,297	1,562	334	1,526	2,258	1,981	1,761	2,253	7,135	8,156	8,640
Noninterest income	9,801	11,430	6,324	7,681	6,970	8,240	8,151	7,666	35,236	31,027	31,114
Noninterest expense	66,216	65,336	63,936	63,577	67,239	82,782	50,076	49,808	259,065	249,905	167,958
Income tax provision	13,109	15,492	14,168	15,266	15,376	7,798	10,182	8,884	58,035	42,240	42,126
Net income	$ 41,098	$ 41,375	$ 38,527	$ 38,718	$ 39,643	$ 28,392	$ 27,303	$ 28,002	$ 158,068	$ 123,340	$ 60,100
Earnings per share:
Basic (in dollars per share)	$ 0.69	$ 0.69	$ 0.62	$ 0.62	$ 0.64	$ 0.46	$ 0.59	$ 0.61	$ 2.62	$ 2.29	$ 1.59
Diluted (in dollars per share)	$ 0.69	$ 0.69	$ 0.62	$ 0.62	$ 0.63	$ 0.46	$ 0.58	$ 0.60	$ 2.60	$ 2.26	$ 1.56