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, 2018 USD ($) securities	Dec. 31, 2017 USD ($) securities
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	2,833	2,127
Estimated Fair Value, Less than 12 Months	$ 5,849	$ 4,777
Gross unrealized loss, less than 12 months	$ (184)	$ (51)
Number of Securities, 12 Months or Greater | securities	2,801	814
Estimated Fair Value, 12 Months or Greater	$ 4,946	$ 1,298
Gross unrealized loss, 12 Months or greater	$ (190)	$ (36)
United States Government Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	5	36
Estimated Fair Value, Less than 12 Months	$ 47	$ 450
Gross unrealized loss, less than 12 months	$ 0	$ (5)
Number of Securities, 12 Months or Greater | securities	25	11
Estimated Fair Value, 12 Months or Greater	$ 79	$ 56
Gross unrealized loss, 12 Months or greater	$ (1)	$ (1)
Government Sponsored Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	8	12
Estimated Fair Value, Less than 12 Months	$ 11	$ 16
Gross unrealized loss, less than 12 months	$ 0	$ 0
Number of Securities, 12 Months or Greater | securities	24	16
Estimated Fair Value, 12 Months or Greater	$ 31	$ 15
Gross unrealized loss, 12 Months or greater	$ (1)	$ 0
States, Municipalities And Political Subdivisions, Tax-Exempt [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	177	414
Estimated Fair Value, Less than 12 Months	$ 295	$ 641
Gross unrealized loss, less than 12 months	$ (3)	$ (5)
Number of Securities, 12 Months or Greater | securities	604	189
Estimated Fair Value, 12 Months or Greater	$ 1,032	$ 356
Gross unrealized loss, 12 Months or greater	$ (19)	$ (7)
Corporate Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	2,185	1,081
Estimated Fair Value, Less than 12 Months	$ 4,503	$ 2,200
Gross unrealized loss, less than 12 months	$ (170)	$ (30)
Number of Securities, 12 Months or Greater | securities	1,220	279
Estimated Fair Value, 12 Months or Greater	$ 2,072	$ 330
Gross unrealized loss, 12 Months or greater	$ (115)	$ (13)
Residential Mortgage-Backed Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	259	445
Estimated Fair Value, Less than 12 Months	$ 383	$ 1,050
Gross unrealized loss, less than 12 months	$ (3)	$ (8)
Number of Securities, 12 Months or Greater | securities	816	287
Estimated Fair Value, 12 Months or Greater	$ 1,458	$ 478
Gross unrealized loss, 12 Months or greater	$ (47)	$ (12)
Commercial Mortgage-Backed Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	6	7
Estimated Fair Value, Less than 12 Months	$ 11	$ 14
Gross unrealized loss, less than 12 months	$ 0	$ 0
Number of Securities, 12 Months or Greater | securities	19	12
Estimated Fair Value, 12 Months or Greater	$ 37	$ 27
Gross unrealized loss, 12 Months or greater	$ (2)	$ (2)
Other Securities [Member]
Investment [Line Items]
Number of Securities, Less than 12 Months | securities	193	132
Estimated Fair Value, Less than 12 Months	$ 599	$ 406
Gross unrealized loss, less than 12 months	$ (8)	$ (3)
Number of Securities, 12 Months or Greater | securities	93	20
Estimated Fair Value, 12 Months or Greater	$ 237	$ 36
Gross unrealized loss, 12 Months or greater	$ (5)	$ (1)