Quarterly Financial Data (unaudited) - Schedule of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ 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	$ 53,369	$ 54,300	$ 54,060	$ 52,364	$ 51,239	$ 49,255	$ 46,460	$ 43,534	$ 214,093		$ 190,488		$ 163,015
Interest expense	10,940	11,655	11,425	10,841	9,862	8,832	7,470	6,262	44,861		32,426		19,839
Net interest income	42,429	42,645	42,635	41,523	41,377	40,423	38,990	37,272	169,232	[1]	158,062	[1]	143,176	[1]
Provision for loan and lease losses	2,227	1,530	2,076	2,685	103	2,745	15,409	2,053	8,518		20,310		9,892
Net interest income after provision for loan and lease losses	40,202	41,115	40,559	38,838	41,274	37,678	23,581	35,219	160,714		137,752		133,284
Noninterest income	16,170	16,599	16,356	16,297	14,416	14,861	15,314	15,582	65,422		60,173		59,240
Total noninterest expense	37,478	36,270	36,778	35,557	33,396	34,371	34,347	35,125	146,083		137,239		130,713
Income before income taxes	18,894	21,444	20,137	19,578	22,294	18,168	4,548	15,676	80,053		60,686		61,811
Income taxes	3,384	3,782	3,669	3,499	3,922	3,204	191	2,826	14,334		10,143		17,717
Net income	$ 15,510	$ 17,662	$ 16,468	$ 16,079	$ 18,372	$ 14,964	$ 4,357	$ 12,850	$ 65,719		$ 50,543		$ 44,094
Weighted average shares outstanding - basic earnings per share	29,232	29,211	29,181	29,146	29,161	29,232	29,176	29,140	29,193		29,177		26,606
Weighted average shares outstanding - diluted earnings per share	29,313	29,285	29,243	29,205	29,220	29,318	29,271	29,234	29,261		29,259		26,708
Net income per share:
Basic (in dollars per share)	$ 0.53	$ 0.60	$ 0.56	$ 0.55	$ 0.63	$ 0.51	$ 0.15	$ 0.44	$ 2.24		$ 1.72		$ 1.64
Diluted (in dollars per share)	0.53	0.60	0.56	0.55	0.63	0.51	0.15	0.44	2.24		1.72		1.64
Dividends per share	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.80		$ 0.80		$ 0.80

[1] Net interest income as well as many other revenues for financial assets and liabilities including loans, leases, securities, and derivatives are excluded from the scope of FASB ASC 606 "Revenue from Contracts with Customers" (FASB ASC 606). Noninterest income streams that are out of scope of FASB ASC 606 include bank owned life insurance income, sales of investment securities and mortgage banking activities.