Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid insurance	$ 11.0	$ 7.8
Prepaid expenses	18.4	21.3
Other receivables and current assets	5.3	6.4
Parts and supplies inventory	9.3	9.3
Prepaid expenses and other current assets	$ 44.0	$ 44.8