Quarterly Financial Information (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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 37,911	$ 34,878	$ 33,652	$ 30,360	$ 28,367	$ 26,004	$ 24,573	$ 21,698	$ 19,212	$ 17,108	$ 14,993	$ 13,158	$ 136,801	$ 100,642	$ 64,471
Interest expense	6,686	6,438	5,757	4,302	3,363	2,841	2,652	2,337	1,778	1,647	1,569	1,287	23,183	11,193	6,281
Net interest income	31,225	28,440	27,895	26,058	25,004	23,163	21,921	19,361	17,434	15,461	13,424	11,871	113,618	89,449	58,190
Provision for loan losses	900	701	1,092	69	1,800	1,231	1,250	400	1,200	570	753	150	2,762	4,681	2,673
Noninterest income	11,376	9,863	9,697	7,783	7,586	15,079	4,910	6,985	9,281	6,868	6,420	6,204	38,719	34,560	28,773
Noninterest expense	28,661	23,393	22,213	24,709	20,191	21,536	19,850	19,417	17,170	16,956	13,974	13,358	98,976	80,994	61,458
Income before taxes on income	13,040	14,209	14,287	9,063	10,599	15,475	5,731	6,529	8,345	4,803	5,117	4,567	50,599	38,334	22,832
Taxes on income	10,767	4,629	4,671	2,950	4,082	5,800	2,407	2,742	3,297	2,041	2,175	1,941	23,017	15,031	9,454
Net income	$ 2,273	$ 9,580	$ 9,616	$ 6,113	$ 6,517	$ 9,675	$ 3,324	$ 3,787	$ 5,048	$ 2,762	$ 2,942	$ 2,626	$ 27,582	$ 23,303	$ 13,378
Net income per share:
Basic	$ 0.06	$ 0.28	$ 0.29	$ 0.19	$ 0.20	$ 0.30	$ 0.10	$ 0.12	$ 0.16	$ 0.11	$ 0.18	$ 0.17	$ 0.80	$ 0.72	$ 0.60
Diluted	$ 0.06	$ 0.27	$ 0.28	$ 0.18	$ 0.19	$ 0.29	$ 0.10	$ 0.11	$ 0.15	$ 0.11	$ 0.17	$ 0.16	$ 0.78	$ 0.70	$ 0.58