Business Combinations, Goodwill and Intangible Assets - Summary of Company's Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 181,272	$ 108,884
Accumulated Amortization	(80,850)	(60,826)
Accumulated Impairment	(5,827)	0
Total	94,595	48,058
Intangible assets, gross	182,172	109,784
Intangible assets, net	95,495	48,958
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	129,790	82,165
Accumulated Amortization	(56,367)	(43,667)
Accumulated Impairment	(5,549)	0
Total	67,874	38,498
Leasehold benefits
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	2,644	2,888
Accumulated Amortization	(2,567)	(2,596)
Accumulated Impairment	0	0
Total	77	292
Developed technology
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	37,154	15,835
Accumulated Amortization	(14,653)	(8,749)
Accumulated Impairment	0	0
Total	22,501	7,086
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	2,045	2,045
Accumulated Amortization	(1,937)	(1,780)
Accumulated Impairment	0	0
Total	108	265
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	9,639	5,951
Accumulated Amortization	(5,326)	(4,034)
Accumulated Impairment	(278)	0
Total	4,035	1,917
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, trade names and trademarks	$ 900	$ 900