Short-Term Debt - Credit Facilities (Detail) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Line Of Credit Facility [Line Items]
Credit Facilities	$ 1,600,000,000	$ 1,200,000,000
Borrowings Outstanding	1,158,000,000	1,019,000,000
Letters of Credit Outstanding	1,000,000	1,000,000
Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Letters of Credit Outstanding	400,000,000	400,000,000
Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	758,000,000	619,000,000
December 13, 2023 [Member] | Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Letters of Credit Outstanding		400,000,000
5-year Facility [Member] | December 17, 2026 [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] | December 17, 2026 [Member] | Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Letters of Credit Outstanding	0	0
5-year Facility [Member] | December 17, 2026 [Member] | Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	758,000,000	619,000,000
1-year Term Facility [Member] | December 13, 2023 [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	400,000,000	400,000,000
Letters of Credit Outstanding	0	0
1-year Term Facility [Member] | December 13, 2023 [Member] | Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Letters of Credit Outstanding	400,000,000
1-year Term Facility [Member] | December 13, 2023 [Member] | Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	0	0
1-year Term Facility [Member] | February 28, 2024 [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	200,000,000	0
Letters of Credit Outstanding	0	0
1-year Term Facility [Member] | February 28, 2024 [Member] | Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Letters of Credit Outstanding	0	0
1-year Term Facility [Member] | February 28, 2024 [Member] | Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	0	0
1-year Term Facility [Member] | April 1, 2024 [Member]
Line Of Credit Facility [Line Items]
Credit Facilities	200,000,000	0
Letters of Credit Outstanding	0	0
1-year Term Facility [Member] | April 1, 2024 [Member] | Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Letters of Credit Outstanding	0	0
1-year Term Facility [Member] | April 1, 2024 [Member] | Commercial Paper [Member]
Line Of Credit Facility [Line Items]
Borrowings Outstanding	$ 0	$ 0