Short-Term Debt - Additional Information (Detail) - USD ($)		3 Months Ended
	Feb. 06, 2020	Mar. 31, 2020	Dec. 31, 2019
Line Of Credit Facility [Line Items]
Weighted-average interest rate		1.72%	2.56%
Line of credit facility maximum borrowing capacity		$ 850,000,000	$ 550,000,000
364-day Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Credit facility maturity period	364 days
Line of credit facility maximum borrowing capacity	$ 300,000,000
Credit facility maturity date	Feb. 04, 2021
Minimum [Member]
Line Of Credit Facility [Line Items]
Commitment fees, percentage		0.125%
Maximum [Member]
Line Of Credit Facility [Line Items]
Commitment fees, percentage		0.35%