Short-Term Debt - Credit Facilities (Detail) - USD ($)	Jun. 30, 2022	Dec. 31, 2021
Line Of Credit Facility [Line Items]
Credit Facilities	$ 1,300,000,000	$ 1,300,000,000
Borrowings Outstanding	500,000,000	745,000,000
Letters of Credit Outstanding	1,000,000	1,000,000
Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	500,000,000	500,000,000
Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	470,000,000	245,000,000
5-year Facility [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	800,000,000	800,000,000
Letters of Credit Outstanding	1,000,000	1,000,000
5-year Facility [Member] | Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	0	0
5-year Facility [Member] | Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	470,000,000	245,000,000
1-year Term Facility [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	500,000,000	500,000,000
Letters of Credit Outstanding	0
1-year Term Facility [Member] | Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	500,000,000	500,000,000
Letters of Credit Outstanding		0
1-year Term Facility [Member] | Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	$ 0	$ 0