Employee Benefit Plans (Estimated Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 10,971	$ 11,256	$ 10,230
Pension Benefits | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,065	9,407
Pension Benefits | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,305	4,704
Pension Benefits | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,904	1,868
Pension Benefits | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,116	990
Pension Benefits | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	114
Pension Benefits | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	248	310
Pension Benefits | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	626	265
Pension Benefits | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	783	1,156
Pension Benefits | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	895	1,101
Pension Benefits | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	997	734
Pension Benefits | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	14
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,778	3,085
Pension Benefits | Level 1 | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,121	2,219
Pension Benefits | Level 1 | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 1 | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,824	1,820
Pension Benefits | Level 1 | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 1 | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 1 | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 1 | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	142	0
Pension Benefits | Level 1 | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	155	399
Pension Benefits | Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	601	826
Pension Benefits | Level 1 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42	26
Pension Benefits | Level 1 | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	14
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,226	7,463
Pension Benefits | Level 2 | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,942	7,188
Pension Benefits | Level 2 | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,305	4,704
Pension Benefits | Level 2 | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	80	48
Pension Benefits | Level 2 | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,115	990
Pension Benefits | Level 2 | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	114
Pension Benefits | Level 2 | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	248	310
Pension Benefits | Level 2 | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	484	265
Pension Benefits | Level 2 | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	627	757
Pension Benefits | Level 2 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	283	275
Pension Benefits | Level 2 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Pension Benefits | Level 2 | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	967	708
Pension Benefits | Level 3 | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	0
Pension Benefits | Level 3 | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 3 | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 3 | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0	0
Pension Benefits | Level 3 | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 3 | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 3 | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Level 3 | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0	3
Pension Benefits | Level 3 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11	0	0
Pension Benefits | Level 3 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	954	708
Pension Benefits | Level 3 | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,443	1,492	$ 1,468
Other Postretirement Benefits | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,387	1,436
Other Postretirement Benefits | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	222	244
Other Postretirement Benefits | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69	51
Other Postretirement Benefits | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51	69
Other Postretirement Benefits | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	2
Other Postretirement Benefits | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	8
Other Postretirement Benefits | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	968	974
Other Postretirement Benefits | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59	88
Other Postretirement Benefits | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55	56
Other Postretirement Benefits | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Other Postretirement Benefits | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	625	622
Other Postretirement Benefits | Level 1 | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	569	566
Other Postretirement Benefits | Level 1 | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 1 | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69	51
Other Postretirement Benefits | Level 1 | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 1 | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 1 | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 1 | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	486	471
Other Postretirement Benefits | Level 1 | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	44
Other Postretirement Benefits | Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55	56
Other Postretirement Benefits | Level 1 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Other Postretirement Benefits | Level 1 | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	818	870
Other Postretirement Benefits | Level 2 | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	818	870
Other Postretirement Benefits | Level 2 | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	222	244
Other Postretirement Benefits | Level 2 | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 2 | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51	69
Other Postretirement Benefits | Level 2 | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	2
Other Postretirement Benefits | Level 2 | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	8
Other Postretirement Benefits | Level 2 | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	482	503
Other Postretirement Benefits | Level 2 | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45	44
Other Postretirement Benefits | Level 2 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 2 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 2 | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Corporate fixed maturity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | U.S. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Foreign government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Federal agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Municipals
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Other (1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Level 3 | Derivative assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0