Summary of Significant Accounting Policies - Schedule of Intangible and Other Assets, Estimated Useful Life (Detail)	12 Months Ended
	Dec. 31, 2017
Minimum | Customer relationships
Summary Of Significant Accounting Policies [Line Items]
Useful life of identifiable intangible assets	5 years
Minimum | Trademarks
Summary Of Significant Accounting Policies [Line Items]
Useful life of identifiable intangible assets	5 years
Maximum | Customer relationships
Summary Of Significant Accounting Policies [Line Items]
Useful life of identifiable intangible assets	15 years
Maximum | Trademarks
Summary Of Significant Accounting Policies [Line Items]
Useful life of identifiable intangible assets	10 years