Fair Value of Financial Instruments (Fair Value of Assets and Liabilities on a Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		$ 233,897	$ 245,265
Liabilities measured at fair value		(1,793)	(3,689)
Benefit Plans' Assets		1,420	1,626
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		1,340	1,692
Benefit Plans' Assets		158	210
Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		227,067	238,376
Liabilities measured at fair value		(317)	(1,631)
Benefit Plans' Assets		1,262	1,416
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		5,490	5,197
Liabilities measured at fair value		(1,476)	(2,058)
Corporate Bonds [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		80,348	82,216
Corporate Bonds [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		77,079	79,125
Corporate Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		3,269	3,091
ABS [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		966	974
ABS [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		937	947
ABS [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		29	27
U.S. Government Bonds [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		417	567
U.S. Government Bonds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		399	556
U.S. Government Bonds [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		18	6
U.S. Government Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value			5
Foreign Government Bonds [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		448	451
Foreign Government Bonds [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		339	341
Foreign Government Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		109	110
RMBS [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		3,373	3,465
RMBS [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		3,366	3,453
RMBS [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		7	12
CMBS [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		804	600
CMBS [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		802	594
CMBS [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		2	6
CLOs [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		1,730	808
CLOs [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		1,625	717
CLOs [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		105	91
State And Municipal Bonds [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		5,345	5,119
State And Municipal Bonds [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		5,345	5,119
Hybrid And Redeemable Preferred Securities [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		593	640
Hybrid And Redeemable Preferred Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		67	71
Hybrid And Redeemable Preferred Securities [Member] | Significant Observable Inputs (Level 2) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		451	493
Hybrid And Redeemable Preferred Securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		75	76
Equity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value			246
Equity AFS Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value			28
Equity AFS Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value			56
Equity AFS Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value			162
Trading Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		1,950	1,620
Trading Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		43	73
Trading Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		1,840	1,498
Trading Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		67	49
Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		99
Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		16
Equity Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		58
Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		25
Derivative Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value	[1]	1,432	1,597
Derivative Investments [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value	[1]	727	994
Derivative Investments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value	[1]	705	603
Other investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		150	150
Other investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		150	150
Invested Cash [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		2,345	1,628
Invested Cash [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		2,345	1,628
GLB Direct Embedded Derivatives [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		123	903
GLB Direct Embedded Derivatives [Member] | Other Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value			(67)
GLB Direct Embedded Derivatives [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		123	903
GLB Direct Embedded Derivatives [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value			(67)
GLB Ceded Embedded Derivatives [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		72	51
GLB Ceded Embedded Derivatives [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		72	51
Indexed Annuity And Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		902
Indexed Annuity And Embedded Derivatives [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value			11
Indexed Annuity And Embedded Derivatives [Member] | Future Contract Benefits [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value		(1,305)	(1,418)
Indexed Annuity And Embedded Derivatives [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		902
Indexed Annuity And Embedded Derivatives [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value			11
Indexed Annuity And Embedded Derivatives [Member] | Significant Unobservable Inputs (Level 3) [Member] | Future Contract Benefits [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value		(1,305)	(1,418)
Separate Account Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		132,800	144,219
Separate Account Assets [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		665	814
Separate Account Assets [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		132,135	143,405
Long-term Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value			(1,127)
Long-term Debt [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value			(1,127)
Reinsurance Related Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value		(3)	(57)
Reinsurance Related Embedded Derivatives [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value		(3)	(57)
Derivative Financial Instruments, Liabilities [Member] | Other Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value	[1]	(485)	(1,020)
Derivative Financial Instruments, Liabilities [Member] | Significant Observable Inputs (Level 2) [Member] | Other Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value	[1]	(314)	(447)
Derivative Financial Instruments, Liabilities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value	[1]	$ (171)	$ (573)

[1] Derivative investment assets and liabilities are presented within the fair value hierarchy on a gross basis by derivative type and not on a master netting basis by counterparty.