Pension Benefits - Schedule of Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 583	$ 524
Defined benefit plan, funded (unfunded) status of plan related to private equity	$ 180
Private Equity
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Fair Value by Hierarchy and NAV [Extensible List]	Fair Value Measured at Net Asset Value Per Share	Fair Value Measured at Net Asset Value Per Share
Private Equity | Minimum
Defined Benefit Plan Disclosure [Line Items]
Period of sale of limited partnership interests in secondary market (in years)	3 months
Private Equity | Maximum
Defined Benefit Plan Disclosure [Line Items]
Period of sale of limited partnership interests in secondary market (in years)	6 months
Real Estate and Other Alternatives
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Fair Value by Hierarchy and NAV [Extensible List]	Fair Value Measured at Net Asset Value Per Share	Fair Value Measured at Net Asset Value Per Share
Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Fair Value by Hierarchy and NAV [Extensible List]	Fair Value Measured at Net Asset Value Per Share	Fair Value Measured at Net Asset Value Per Share
Period of liquidation (in years)	18 months
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 15,278	$ 15,404	$ 14,979	$ 18,504
Pension Benefits | U.S. Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	2,752	2,475
Pension Benefits | International Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	1,508	1,584
Pension Benefits | U.S. Government Issued Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	619	615
Pension Benefits | Corporate Bonds Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	5,429	5,526
Pension Benefits | Structured Assets Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	159	132
Pension Benefits | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	783	735
Pension Benefits | Commingled Trust Fund
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	478	475
Pension Benefits | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	343	338
Pension Benefits | Futures
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	(4)	19
Pension Benefits | Private Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	975	1,031
Pension Benefits | Real Estate and Other Alternatives
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	1,609	1,876
Pension Benefits | Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	788	723
Pension Benefits | Total Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	(179)	(193)
Pension Benefits | Pending Activities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	18	68
Pension Benefits | Fair Value, Inputs, Level 1 and 2 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	12,067	11,899
Pension Benefits | Fair Value, Inputs, Level 1 and 2 | Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	(140)	(148)
Pension Benefits | Fair Value, Inputs, Level 1 and 2 | Investments Excluding Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	15,260	15,336
Pension Benefits | Level 1 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	4,307	4,113
Pension Benefits | Level 1 | U.S. Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	2,752	2,474
Pension Benefits | Level 1 | International Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	1,508	1,584
Pension Benefits | Level 1 | U.S. Government Issued Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Corporate Bonds Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Structured Assets Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Commingled Trust Fund
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	51	36
Pension Benefits | Level 1 | Futures
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	(4)	19
Pension Benefits | Level 1 | Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	(50)	(52)
Pension Benefits | Level 1 | Investments Excluding Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	4,257	4,061
Pension Benefits | Level 2 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	7,760	7,786
Pension Benefits | Level 2 | U.S. Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	1
Pension Benefits | Level 2 | U.S. Government Issued Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	619	615
Pension Benefits | Level 2 | Corporate Bonds Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	5,429	5,526
Pension Benefits | Level 2 | Structured Assets Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	159	132
Pension Benefits | Level 2 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	783	735
Pension Benefits | Level 2 | Commingled Trust Fund
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	478	475
Pension Benefits | Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	292	302
Pension Benefits | Level 2 | Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	(90)	(96)
Pension Benefits | Level 2 | Investments Excluding Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	7,670	7,690
Pension Benefits | Fair Value Measured at Net Asset Value Per Share | Investments Valued Using NAV Per Share
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	3,372	3,630
Pension Benefits | Fair Value Measured at Net Asset Value Per Share | Funds For Retiree Health Benefits Measured At Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ (39)	$ (45)