Summary of Significant Accounting Policies - Amortization of Intangible Assets, Useful Life (Detail)	12 Months Ended
	Dec. 31, 2017
Customer Relationships [Member] | Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets, estimated useful life	5 years
Customer Relationships [Member] | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets, estimated useful life	11 years
Research Content [Member] | Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets, estimated useful life	1 year
Research Content [Member] | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets, estimated useful life	2 years
Technology [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets, estimated useful life	7 years