Quarterly Results of Operations (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	$ 136,021	$ 128,876	$ 92,699	$ 90,827	$ 85,684	$ 70,161	$ 68,733	$ 45,427	$ 448,423	$ 270,005	$ 166,605
Interest expense	18,475	16,163	11,528	9,546	7,514	5,870	5,395	3,724	55,712	22,503	13,530
Provision for credit losses	2,258	1,981	1,761	2,253	2,194	2,049	1,945	2,244	8,156	8,640	8,776
Noninterest income	6,970	8,240	8,151	7,666	9,451	8,221	8,759	4,683	31,027	31,114	19,602
Noninterest expense	67,239	82,782	50,076	49,808	49,886	39,612	48,455	30,005	249,905	167,958	98,063
Income tax provision	15,376	7,798	10,182	8,884	19,370	10,619	7,521	4,616	42,240	42,126	25,215
Net income	$ 39,643	$ 28,392	$ 27,303	$ 28,002	$ 16,171	$ 20,232	$ 14,176	$ 9,521	$ 123,340	$ 60,100	$ 40,103
Earnings per share:
Basic (in dollars per share)	$ 0.64	$ 0.46	$ 0.59	$ 0.61	$ 0.37	$ 0.46	$ 0.36	$ 0.35	$ 2.29	$ 1.59	$ 1.49
Diluted (in dollars per share)	$ 0.63	$ 0.46	$ 0.58	$ 0.60	$ 0.36	$ 0.46	$ 0.35	$ 0.34	$ 2.26	$ 1.56	$ 1.46