Derivatives - Fair Value Hedge (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2021
Interest rate contracts
Derivatives
Derivative, notional amount		$ 800,000,000
Floating rate registered note due 2049
Derivatives
Principal amount		500,000,000
Floating rate registered note due 2050 | L I B O R
Derivatives
Principal amount		300,000,000
Fixed rate registered note due 2049
Derivatives
Principal amount	$ 500,000,000	1,000,000,000
Fixed rate registered note due 2050
Derivatives
Principal amount	350,000,000	$ 650,000,000
Fixed rate 30-year debenture due 2028
Derivatives
Principal amount	$ 220,000,000