Quarterly Consolidated Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Interest income	$ 33,550	$ 31,963	$ 30,299	$ 28,905	$ 28,527	$ 28,081	$ 27,458	$ 24,036	$ 124,717	$ 108,102	$ 87,383
Interest expense	5,058	4,434	3,752	3,218	3,140	3,074	2,826	2,391	16,462	11,431	8,440
Net interest income	28,492	27,529	26,547	25,687	25,387	25,007	24,632	21,645	108,255	96,671	78,943
Provision for loan losses	472	1,376	423	(1,095)	314	462	2,118	55	1,176	2,949	283
Net interest income after provision for loan losses	28,020	26,153	26,124	26,782	25,073	24,545	22,514	21,590	107,079	93,722	78,660
Gain on sale, call or write-down of securities	97	76	0	0	159	158	267	0	173	584	509
Noninterest income	8,272	9,846	10,214	10,703	9,738	9,337	9,873	10,549	39,208	40,081	34,030
Noninterest expense	21,210	22,286	22,665	23,251	21,139	20,440	20,630	23,142	89,412	85,351	71,093
Income before income taxes	15,179	13,789	13,673	14,234	13,831	13,600	12,024	8,997	56,875	48,452	41,597
Income taxes	3,082	2,483	2,564	2,497	4,431	4,219	3,677	3,857	10,626	16,184	12,754
Net income	$ 12,097	$ 11,306	$ 11,109	$ 11,737	$ 9,400	$ 9,381	$ 8,347	$ 5,140	$ 46,249	$ 32,268	$ 28,843
Earnings per common share:
Basic	$ 0.60	$ 0.55	$ 0.54	$ 0.58	$ 0.47	$ 0.46	$ 0.41	$ 0.27	$ 2.27	$ 1.62	$ 1.61
Diluted	$ 0.59	$ 0.55	$ 0.54	$ 0.58	$ 0.46	$ 0.46	$ 0.41	$ 0.27	$ 2.26	$ 1.61	$ 1.60
Average shares outstanding:
Basic	20,313	20,400	20,388	20,330	20,310	20,298	20,294	18,870	20,349	19,932	17,938
Diluted	20,404	20,467	20,492	20,438	20,444	20,418	20,408	18,980	20,349	19,932	17,938