Quarterly Financial Data - Summary of Quarterly Results (Detail) - USD ($) $ / shares in Units, $ 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]
Revenues, net	$ 256,872	$ 251,392	$ 243,509	$ 239,573	$ 234,903	$ 231,124	$ 210,112	$ 206,973	$ 991,346		$ 883,112		$ 762,310
Gross profit	88,610	83,850	81,063	82,333	79,955	78,967	70,463	68,872	335,856	[1]	298,257	[1]	267,168	[1]
Net income	$ 21,356	$ 19,044	$ 12,564	$ 14,695	$ 3,857	$ 15,249	$ 14,462	$ 23,158	$ 67,659		$ 56,726		$ 48,888
Earnings per share:
Basic (in dollars per share)	$ 0.62	$ 0.55	$ 0.36	$ 0.43	$ 0.11	$ 0.44	$ 0.42	$ 0.67	$ 1.97		$ 1.65		$ 1.44
Diluted (in dollars per share)	$ 0.62	$ 0.55	$ 0.36	$ 0.42	$ 0.11	$ 0.43	$ 0.41	$ 0.66	$ 1.95		$ 1.62		$ 1.39
Weighted-average number of shares used in computing earnings per share:
Basic (in shares)	34,253,308	34,322,449	34,451,671	34,374,815	34,388,025	34,458,520	34,511,777	34,446,265	34,350,150		34,451,008		33,897,916
Diluted (in shares)	34,696,896	34,699,497	34,702,547	34,833,435	34,921,388	35,207,991	35,142,388	35,302,926	34,732,683		35,030,984		35,110,210
Stock compensation expense	$ 4,532	$ 7,427	$ 7,155	$ 6,956	$ 6,590	$ 5,344	$ 6,893	$ 5,074	$ 26,070		$ 23,901		$ 23,041
Amortization of intangibles	$ 4,974	$ 5,502	$ 5,554	$ 5,528	$ 5,951	$ 6,718	$ 3,761	$ 3,947	$ 21,558		$ 20,377		$ 13,975

[1] Exclusive of depreciation and amortization expense.