Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 85,684	$ 70,161	$ 68,733	$ 45,427	$ 45,797	$ 42,429	$ 40,874	$ 37,505	$ 270,005	$ 166,605	$ 118,356
Interest expense	7,514	5,870	5,395	3,724	3,493	3,420	3,313	3,304	22,503	13,530	12,057
Provision for loan losses	2,185	2,049	1,904	2,502	2,054	4,013	1,589	1,120	8,640	8,776	6,425
Noninterest income	9,451	8,221	8,759	4,683	4,318	5,968	4,468	4,848	31,114	19,602	14,388
Noninterest expense	49,895	39,612	48,496	29,747	25,377	25,860	23,713	23,633	167,750	98,583	73,538
Income tax provision	19,370	10,619	7,521	4,616	7,238	5,877	6,358	5,742	42,126	25,215	15,209
Net income	$ 16,171	$ 20,232	$ 14,176	$ 9,521	$ 11,953	$ 9,227	$ 10,369	$ 8,554	$ 60,100	$ 40,103	$ 25,515
Earnings per share:
Basic (in dollars per share)	$ 0.37	$ 0.51	$ 0.36	$ 0.35	$ 0.44	$ 0.34	$ 0.38	$ 0.33	$ 1.59	$ 1.49	$ 1.21
Diluted (in dollars per share)	$ 0.36	$ 0.50	$ 0.35	$ 0.34	$ 0.43	$ 0.33	$ 0.37	$ 0.33	$ 1.56	$ 1.46	$ 1.19