Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Line Items]
Capital lease assets	$ 62.8	$ 63.4
Assets fully depreciated	24.8	26.8
Capital leased assets, net book value	11.7	13.0
Other Non-Current Assets [Member]
Commitments And Contingencies Disclosure [Line Items]
Insurance receivable and indemnification asset	$ 2.8	$ 2.8
Minimum [Member]
Commitments And Contingencies Disclosure [Line Items]
Estimated life of capital lease	4 years
Noncancellable operating leases, renewal period	1 year
Maximum [Member]
Commitments And Contingencies Disclosure [Line Items]
Estimated life of capital lease	6 years
Noncancellable operating leases, renewal period	5 years