Retirement Benefits - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Obligation, Pension Benefits	$ 98
Increase (Decrease) in Obligation, Other Postretirement Benefits	1
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	25
Defined Benefit Plan Amounts Recognized In Regulatory Assets Before Tax	66
Defined Benefit Plan Amounts Recognized In Regulatory Liabilities Before Tax	$ 2
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets	7.00%
Discount rate	5.19%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets	6.50%
Discount rate	5.17%