Employee Benefits - Derivative Instruments (Details) - Combined Pension Plan - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Exchange-traded U.S. equity futures
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	$ 60	$ 70
Exchange-traded Treasury and other interest rate futures
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	1,136	1,256
Exchange-traded Foreign currency futures
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	1	2
Interest rate swaps
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	214	82
Credit default swaps
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	72	139
Index swaps
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	94	90
Foreign exchange forwards
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	57	50
Options
Defined Benefit Plan Disclosure [Line Items]
Derivative, notional amount	$ 32	$ 251