Commitments and Contingencies - Schedule of Future Minimum Contracts of Affreightment and Royalty Commitments for All Noncancelable Agreements (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
2020	$ 15.8
2021	16.1
2022	16.3
2023	16.6
2024	16.9
Thereafter	52.2
Total	133.9
2020	15.7
2021	11.1
2022	10.3
2023	9.2
2024	8.9
Thereafter	59.7
Total	$ 114.9	$ 119.9