Fair Value Measurement - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior secured credit facilities	$ 889.9	$ 893.2
Level 2 | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	635.3	577.6
First Lien Credit Facility due 2023 | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior secured credit facilities	635.3	641.8
Second Lien Credit Facility due 2024 | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	254.3	236.7
Senior secured credit facilities	$ 254.6	$ 251.4