Financial Instruments - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) Customer	Sep. 30, 2020 Customer	Sep. 30, 2021 USD ($) Customer	Sep. 30, 2020 Customer	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Long-term debt, carrying values	$ 5,119.5		$ 5,119.5		$ 2,625.8
Long-term debt, fair values	$ 5,490.0		$ 5,490.0		$ 3,080.0
Customer Concentration Risk | Total Revenues
Debt Instrument [Line Items]
Number of customer accounted for 10% or more of consolidated total revenues | Customer	0	0	0	0
Customer Concentration Risk | Total Revenues | Minimum
Debt Instrument [Line Items]
Percentage of concentration risk	10.00%	10.00%	10.00%	10.00%