Fair Value Measurement - Fair Value, Valuation Techniques and Related Unobservable Inputs for Level Three (Detail) - Customer Relationships - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 11.0	$ 4.9
Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 4.6
Discount rate	13.00%
Attrition rate	5.00%	2.70%
Fair Value, Inputs, Level 3 | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rate			12.00%
Attrition rate			6.60%
Fair Value, Inputs, Level 3 | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rate			18.00%
Attrition rate			12.00%