Cash Flow Information - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Significant Noncash Transactions [Line Items]
Cash paid for interest		$ 46.6	$ 41.9
Net of capitalized interest		1.8	7.0
Line of credit facilities gross borrowings		120.0	181.0
Line of credit facilities gross repayments		0.0	33.0
Line of credit facilities gross repayments on term loans		12.0	0.0
Decrease in accrued construction costs		$ 6.3	$ 15.7
Common Stock
Other Significant Noncash Transactions [Line Items]
Conversion of units, shares issued (in shares)	6,250,000