Pension Plans, Retirement Benefits and Savings Plans (Details) - Fair Value - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension Plans [Member]
Defined benefit plan disclosure
Fair value of plan assets	$ 4,334	$ 4,246	$ 4,033
Pension Plans [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	3,379	3,272
Pension Plans [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	954	973
Pension Plans [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1	1
Pension Plans [Member] | Fixed maturities [Member]
Defined benefit plan disclosure
Fair value of plan assets	902	921
Pension Plans [Member] | Fixed maturities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Fixed maturities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	902	921
Pension Plans [Member] | Fixed maturities [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member]
Defined benefit plan disclosure
Fair value of plan assets	109	105
Pension Plans [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	109	105
Pension Plans [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Debt securities issued by foreign governments [Member]
Defined benefit plan disclosure
Fair value of plan assets	34	32
Pension Plans [Member] | Debt securities issued by foreign governments [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Debt securities issued by foreign governments [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	34	32
Pension Plans [Member] | Debt securities issued by foreign governments [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	8	8
Pension Plans [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	8	8
Pension Plans [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Corporate and all other bonds [Member]
Defined benefit plan disclosure
Fair value of plan assets	751	776
Pension Plans [Member] | Corporate and all other bonds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Corporate and all other bonds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	751	776
Pension Plans [Member] | Corporate and all other bonds [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Total mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,845	1,865
Pension Plans [Member] | Total mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,808	1,856
Pension Plans [Member] | Total mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	37	9
Pension Plans [Member] | Total mutual funds [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Equity mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,178	1,207
Pension Plans [Member] | Equity mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,172	1,201
Pension Plans [Member] | Equity mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	6	6
Pension Plans [Member] | Equity mutual funds [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Bond mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	667	658
Pension Plans [Member] | Bond mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	636	655
Pension Plans [Member] | Bond mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	31	3
Pension Plans [Member] | Bond mutual funds [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Equity securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,401	1,302
Pension Plans [Member] | Equity securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,401	1,302
Pension Plans [Member] | Equity securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Equity securities [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Other investments [Member]
Defined benefit plan disclosure
Fair value of plan assets	1	1
Pension Plans [Member] | Other investments [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Other investments [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Other investments [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1	1
Pension Plans [Member] | Cash and short-term securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	185	157
Pension Plans [Member] | Cash and short-term securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	170	114
Pension Plans [Member] | Cash and short-term securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	15	43
Pension Plans [Member] | Cash and short-term securities [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Cash and short-term securities, U.S. Treasury securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	108	0
Pension Plans [Member] | Cash and short-term securities, U.S. Treasury securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	108	0
Pension Plans [Member] | Cash and short-term securities, U.S. Treasury securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Cash and short-term securities, U.S. Treasury securities [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Pension Plans [Member] | Cash and short-term securities, other [Member]
Defined benefit plan disclosure
Fair value of plan assets	77	157
Pension Plans [Member] | Cash and short-term securities, other [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	62	114
Pension Plans [Member] | Cash and short-term securities, other [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	15	43
Pension Plans [Member] | Cash and short-term securities, other [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	0
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Fair value of plan assets	6	7	$ 8
Postretirement Benefit Plans [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	$ 6	$ 7