Investments (Current And Long-Term Fixed Maturity Securities, Available-For-Sale) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Investments [Line Items]
Gross Unrealized Gains	$ 770		$ 170
Fixed Maturities [Member]
Investments [Line Items]
Cost or Amortized Cost	19,767	$ 17,380
Gross Unrealized Gains	770	173
Gross Unrealized Losses, Less than 12 Months	(24)	(184)
Gross Unrealized Losses, 12 Months or Greater	(35)	(190)
Available-for-sale Securities	20,478	17,179
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	(5)	(3)
Fixed Maturities [Member] \| United States Government Securities [Member]
Investments [Line Items]
Cost or Amortized Cost	487	414
Gross Unrealized Gains	10	3
Gross Unrealized Losses, Less than 12 Months	0	0
Gross Unrealized Losses, 12 Months or Greater	0	(1)
Available-for-sale Securities	497	416
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	0	0
Fixed Maturities [Member] \| Government Sponsored Securities [Member]
Investments [Line Items]
Cost or Amortized Cost	125	108
Gross Unrealized Gains	6	1
Gross Unrealized Losses, Less than 12 Months	0	0
Gross Unrealized Losses, 12 Months or Greater	0	(1)
Available-for-sale Securities	131	108
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	0	0
Fixed Maturities [Member] \| States, Municipalities And Political Subdivisions, Tax-Exempt [Member]
Investments [Line Items]
Cost or Amortized Cost	4,469	4,716
Gross Unrealized Gains	275	91
Gross Unrealized Losses, Less than 12 Months	(1)	(3)
Gross Unrealized Losses, 12 Months or Greater	(1)	(19)
Available-for-sale Securities	4,742	4,785
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	0	0
Fixed Maturities [Member] \| Corporate Securities [Member]
Investments [Line Items]
Cost or Amortized Cost	9,040	8,189
Gross Unrealized Gains	341	33
Gross Unrealized Losses, Less than 12 Months	(17)	(170)
Gross Unrealized Losses, 12 Months or Greater	(25)	(115)
Available-for-sale Securities	9,339	7,937
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	(5)	(3)
Fixed Maturities [Member] \| Residential Mortgage-Backed Securities [Member]
Investments [Line Items]
Cost or Amortized Cost	3,914	2,769
Gross Unrealized Gains	111	31
Gross Unrealized Losses, Less than 12 Months	(4)	(3)
Gross Unrealized Losses, 12 Months or Greater	(4)	(47)
Available-for-sale Securities	4,017	2,750
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	0	0
Fixed Maturities [Member] \| Commercial Mortgage-Backed Securities [Member]
Investments [Line Items]
Cost or Amortized Cost	87	69
Gross Unrealized Gains	3	0
Gross Unrealized Losses, Less than 12 Months	0	0
Gross Unrealized Losses, 12 Months or Greater	0	(2)
Available-for-sale Securities	90	67
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	0	0
Fixed Maturities [Member] \| Other Securities [Member]
Investments [Line Items]
Cost or Amortized Cost	1,645	1,115
Gross Unrealized Gains	24	14
Gross Unrealized Losses, Less than 12 Months	(2)	(8)
Gross Unrealized Losses, 12 Months or Greater	(5)	(5)
Available-for-sale Securities	1,662	1,116
Non-Credit Component of Other-Than-Temporary Impairments Recognized in Accumulated Other Comprehensive Income	$ 0	$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of other than temporary impairment (OTTI) on investment in available-for-sale debt security, recognized in other comprehensive loss, attributable to parent entity.

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