Debt - Schedule of Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Carrying Amount [Member] | Senior Secured Credit Facilities [Member]
Financial liabilities:
Credit facility	$ 4,304.5	$ 4,485.9
Carrying Amount [Member] | 5.5% Senior Notes due 2027 [Member]
Financial liabilities:
Senior notes	2,000.0	2,000.0
Carrying Amount [Member] | Other Indebtedness [Member]
Financial liabilities:
Credit facility	11.4	10.1
Fair Value [Member] | Senior Secured Credit Facilities [Member]
Financial liabilities:
Credit facility	4,251.5	4,426.0
Fair Value [Member] | 5.5% Senior Notes due 2027 [Member]
Financial liabilities:
Credit facility	2,119.4	2,136.0
Fair Value [Member] | Other Indebtedness [Member]
Financial liabilities:
Credit facility	$ 11.5	$ 10.2