Short-Term and Long-Term Debt - Credit Facilities and Letters of Credit (Details)	Dec. 31, 2023 USD ($)
Line of Credit Facility [Line Items]
Maximum Available	$ 3,835,000,000
LOCs Issued	1,902,000,000
Five-year revolving credit facility
Line of Credit Facility [Line Items]
Maximum Available	2,000,000,000
LOCs Issued	126,000,000
LOC facility, due August 2031
Line of Credit Facility [Line Items]
Maximum Available	976,000,000
LOCs Issued	917,000,000
LOC facility, due October 2031
Line of Credit Facility [Line Items]
Maximum Available	859,000,000
LOCs Issued	$ 859,000,000