Investments (Aggregate Fair Value And Gross Unrealized Loss Of Fixed Maturity Securities And Equity Securities In An Unrealized Loss Position) (Details) - Fixed Maturity Securities [Member] $ in Millions	Dec. 31, 2020 USD ($) securities	Dec. 31, 2019 USD ($) securities
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	1,201	1,029
Estimated Fair Value, Less than 12 Months	$ 2,125	$ 2,179
Gross unrealized loss, less than 12 months	$ (39)	$ (24)
Number of Securities, 12 Months or Greater | securities	333	549
Estimated Fair Value, 12 Months or Greater	$ 469	$ 902
Gross unrealized loss, 12 Months or greater	$ (29)	$ (23)
United States Government Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	27	27
Estimated Fair Value, Less than 12 Months	$ 301	$ 250
Gross unrealized loss, less than 12 months	$ (2)	$ (3)
Number of Securities, 12 Months or Greater | securities	0	2
Estimated Fair Value, 12 Months or Greater	$ 0	$ 1
Gross unrealized loss, 12 Months or greater	$ 0	$ 0
Government Sponsored Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	0	14
Estimated Fair Value, Less than 12 Months	$ 0	$ 12
Gross unrealized loss, less than 12 months	$ 0	$ 0
Number of Securities, 12 Months or Greater | securities	1	3
Estimated Fair Value, 12 Months or Greater	$ 0	$ 1
Gross unrealized loss, 12 Months or greater	$ 0	$ 0
Foreign Government Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	55
Estimated Fair Value, Less than 12 Months	$ 35
Gross unrealized loss, less than 12 months	$ (2)
Number of Securities, 12 Months or Greater | securities	9
Estimated Fair Value, 12 Months or Greater	$ 4
Gross unrealized loss, 12 Months or greater	$ 0
States, Municipalities And Political Subdivisions, Tax-Exempt [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	36	114
Estimated Fair Value, Less than 12 Months	$ 57	$ 306
Gross unrealized loss, less than 12 months	$ (1)	$ (3)
Number of Securities, 12 Months or Greater | securities	1	14
Estimated Fair Value, 12 Months or Greater	$ 3	$ 11
Gross unrealized loss, 12 Months or greater	$ 0	$ 0
Corporate Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	646	386
Estimated Fair Value, Less than 12 Months	$ 765	$ 558
Gross unrealized loss, less than 12 months	$ (20)	$ (9)
Number of Securities, 12 Months or Greater | securities	150	224
Estimated Fair Value, 12 Months or Greater	$ 169	$ 286
Gross unrealized loss, 12 Months or greater	$ (11)	$ (15)
Residential Mortgage-Backed Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	224	321
Estimated Fair Value, Less than 12 Months	$ 442	$ 635
Gross unrealized loss, less than 12 months	$ (8)	$ (6)
Number of Securities, 12 Months or Greater | securities	90	189
Estimated Fair Value, 12 Months or Greater	$ 110	$ 237
Gross unrealized loss, 12 Months or greater	$ (9)	$ (3)
Commercial Mortgage-Backed Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	6	1
Estimated Fair Value, Less than 12 Months	$ 16	$ 3
Gross unrealized loss, less than 12 months	$ (1)	$ 0
Number of Securities, 12 Months or Greater | securities	3	4
Estimated Fair Value, 12 Months or Greater	$ 4	$ 8
Gross unrealized loss, 12 Months or greater	$ (3)	$ 0
Other Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	207	166
Estimated Fair Value, Less than 12 Months	$ 509	$ 415
Gross unrealized loss, less than 12 months	$ (5)	$ (3)
Number of Securities, 12 Months or Greater | securities	79	113
Estimated Fair Value, 12 Months or Greater	$ 179	$ 358
Gross unrealized loss, 12 Months or greater	$ (6)	$ (5)