Pension Plans, Retirement Benefits and Savings Plans (Details) - Fair Value - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Plans [Member]
Defined benefit plan disclosure
Fair value of plan assets	$ 4,033	$ 5,036	$ 4,756
Pension Plans [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	3,149	4,239
Pension Plans [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	883	796
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	822	748
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	822	748
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	80	26
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	80	26
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	25	38
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	25	38
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	4	6
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	4	6
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	713	678
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	713	678
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	1,911	2,759
Pension Plans [Member] | Total mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,902	2,749
Pension Plans [Member] | Total mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	9	10
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	1,157	1,645
Pension Plans [Member] | Equity mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,151	1,638
Pension Plans [Member] | Equity mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	6	7
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	754	1,114
Pension Plans [Member] | Bond mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	751	1,111
Pension Plans [Member] | Bond mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	3	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	1,116	1,385
Pension Plans [Member] | Equity securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,116	1,384
Pension Plans [Member] | Equity securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	0	1
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	183	143
Pension Plans [Member] | Cash and short-term securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	131	106
Pension Plans [Member] | Cash and short-term securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	52	37
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	0	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	0	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	183	143
Pension Plans [Member] | Cash and short-term securities, other [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	131	106
Pension Plans [Member] | Cash and short-term securities, other [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	52	37
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	8	9	$ 11
Postretirement Benefit Plans [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	$ 8	$ 9