Quarterly Financial Data (Unaudited) - Summary of Quarterly Results (Detail) - USD ($) $ / shares in Units, $ 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
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Revenues, net	$ 234,903	$ 231,124	$ 210,112	$ 206,973	$ 197,875	$ 192,345	$ 189,057	$ 183,033	$ 883,112		$ 762,310	[1]	$ 685,988	[1]
Gross profit(1)	79,955	78,967	70,463	68,872	68,616	69,268	65,323	63,961	298,257	[2]	267,168	[1],[2]	238,270	[1],[2]
Net income	$ 3,857	$ 15,249	$ 14,462	$ 23,158	$ (9,355)	$ 21,077	$ 20,378	$ 16,788	$ 56,726		$ 48,888	[1],[3]	$ 61,733	[1],[3]
Earnings per share:
Basic (in dollars per share)	$ 0.11	$ 0.44	$ 0.42	$ 0.67	$ (0.27)	$ 0.62	$ 0.60	$ 0.50	$ 1.65		$ 1.44	[1]	$ 1.84	[1]
Diluted (in dollars per share)	$ 0.11	$ 0.43	$ 0.41	$ 0.66	$ (0.27)	$ 0.60	$ 0.58	$ 0.48	$ 1.62		$ 1.39	[1]	$ 1.79	[1]
Weighted-average number of shares used in computing earnings per share:
Basic (in shares)	34,388,025	34,458,520	34,511,777	34,446,265	34,086,711	33,838,374	33,819,320	33,845,560	34,451,008		33,897,916	[1]	33,566,367	[1]
Diluted (in shares)	34,921,388	35,207,991	35,142,388	35,302,926	34,086,711	35,043,987	34,993,226	35,108,882	35,030,984		35,110,210	[1]	34,563,319	[1]
Stock compensation expense	$ 6,590	$ 5,344	$ 6,893	$ 5,074	$ 6,270	$ 5,708	$ 5,107	$ 5,956	$ 23,901		$ 23,041		$ 19,770
Amortization of intangibles	$ 5,951	$ 6,718	$ 3,761	$ 3,947	$ 3,483	$ 3,487	$ 3,507	$ 3,498	$ 20,377		$ 13,975		$ 11,873
Weighted average potentially dilutive shares considered anti-dilutive and not included in computing diluted earnings per share (in shares)									121,344		151,961		92,538
Convertible Debt Securities
Weighted-average number of shares used in computing earnings per share:
Weighted average potentially dilutive shares considered anti-dilutive and not included in computing diluted earnings per share (in shares)					0

[1] Adjusted pursuant to adoption of ASU No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost. Refer to Note 21 and Note 27 to the consolidated financial statements.

[2] Exclusive of depreciation and amortization.

[3] Adjusted pursuant to adoption of ASU 2016-18, Statements of Cash Flows, Restricted Cash. Refer to Note 8 and Note 27 to the consolidated financial statements.