Summary of Significant Accounting Policies - Summary of Lived Intangible Assets Amortized over their Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2017
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	3 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	15 years
Leasehold benefits | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	3 years
Leasehold benefits | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	8 years
Developed technology | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	5 years
Developed technology | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	10 years
Non-compete agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	1 year
Non-compete agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	5 years
Trade names and trademarks | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	3 years
Trade names and trademarks | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangible assets	10 years