Other Noncurrent Assets - Schedule of Maturities of Lease Liabilities (Detail) $ in Millions	Mar. 31, 2019 USD ($)
Gross amounts due each year:
2019 (remainder of year)	$ 5.8
2020	6.7
2021	6.0
2022	3.4
2023	2.2
2024 and thereafter	21.3
Total lease payments	45.4
Less imputed interest	13.0
Total lease obligations	32.4
Less current obligations	6.8
Long-term lease obligations	$ 25.6