Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Apr. 04, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cost of debt, discount period	3 years
Contingent liability, current	$ 2.3
Contingent liability, noncurrent	$ 13.6
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cost of debt, discount rate	3.78%
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cost of debt, discount rate	4.93%
Headway
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Ownership Interest acquired		100.00%
Fair value of contingent consideration	$ 15.9	$ 15.9