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, 2019 USD ($) securities	Dec. 31, 2018 USD ($) securities
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	1,029	2,833
Estimated Fair Value, Less than 12 Months	$ 2,179	$ 5,849
Gross unrealized loss, less than 12 months	$ (24)	$ (184)
Number of Securities, 12 Months or Greater | securities	549	2,801
Estimated Fair Value, 12 Months or Greater	$ 902	$ 4,946
Gross unrealized loss, 12 Months or greater	$ (23)	$ (190)
United States Government Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	27	5
Estimated Fair Value, Less than 12 Months	$ 250	$ 47
Gross unrealized loss, less than 12 months	$ (3)	$ 0
Number of Securities, 12 Months or Greater | securities	2	25
Estimated Fair Value, 12 Months or Greater	$ 1	$ 79
Gross unrealized loss, 12 Months or greater	$ 0	$ (1)
Government Sponsored Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	14	8
Estimated Fair Value, Less than 12 Months	$ 12	$ 11
Gross unrealized loss, less than 12 months	$ 0	$ 0
Number of Securities, 12 Months or Greater | securities	3	24
Estimated Fair Value, 12 Months or Greater	$ 1	$ 31
Gross unrealized loss, 12 Months or greater	$ 0	$ (1)
States, Municipalities And Political Subdivisions, Tax-Exempt [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	114	177
Estimated Fair Value, Less than 12 Months	$ 306	$ 295
Gross unrealized loss, less than 12 months	$ (3)	$ (3)
Number of Securities, 12 Months or Greater | securities	14	604
Estimated Fair Value, 12 Months or Greater	$ 11	$ 1,032
Gross unrealized loss, 12 Months or greater	$ 0	$ (19)
Corporate Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	386	2,185
Estimated Fair Value, Less than 12 Months	$ 558	$ 4,503
Gross unrealized loss, less than 12 months	$ (9)	$ (170)
Number of Securities, 12 Months or Greater | securities	224	1,220
Estimated Fair Value, 12 Months or Greater	$ 286	$ 2,072
Gross unrealized loss, 12 Months or greater	$ (15)	$ (115)
Residential Mortgage-Backed Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	321	259
Estimated Fair Value, Less than 12 Months	$ 635	$ 383
Gross unrealized loss, less than 12 months	$ (6)	$ (3)
Number of Securities, 12 Months or Greater | securities	189	816
Estimated Fair Value, 12 Months or Greater	$ 237	$ 1,458
Gross unrealized loss, 12 Months or greater	$ (3)	$ (47)
Commercial Mortgage-Backed Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	1	6
Estimated Fair Value, Less than 12 Months	$ 3	$ 11
Gross unrealized loss, less than 12 months	$ 0	$ 0
Number of Securities, 12 Months or Greater | securities	4	19
Estimated Fair Value, 12 Months or Greater	$ 8	$ 37
Gross unrealized loss, 12 Months or greater	$ 0	$ (2)
Other Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	166	193
Estimated Fair Value, Less than 12 Months	$ 415	$ 599
Gross unrealized loss, less than 12 months	$ (3)	$ (8)
Number of Securities, 12 Months or Greater | securities	113	93
Estimated Fair Value, 12 Months or Greater	$ 358	$ 237
Gross unrealized loss, 12 Months or greater	$ (5)	$ (5)