Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Interest Rate Swap
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities		$ 4.8
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	$ 15.9
Fair Value, Measurements, Recurring | Interest Rate Swap
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities		4.8
Fair Value, Measurements, Recurring | Level 2 | Interest Rate Swap
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities		$ 4.8
Fair Value, Measurements, Recurring | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	$ 15.9