Fair Value of Financial Instruments (Fair Value of Assets and Liabilities on a Recurring Basis) (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		$ 249,473	$ 233,897
Liabilities measured at fair value		(2,674)	(1,793)
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		1,435	1,340
Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		241,855	227,067
Liabilities measured at fair value		(531)	(317)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		6,183	5,490
Liabilities measured at fair value		(2,143)	(1,476)
Corporate Bonds [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		83,208	80,348
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		79,687	77,079
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		3,521	3,269
ABS [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		1,047	966
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		966	937
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		81	29
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		423	417
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		405	399
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	18
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		453	448
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		343	339
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		110	109
RMBS [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		3,414	3,373
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		3,414	3,366
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
CMBS [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		885	804
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		883	802
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	2
CLOs [Member] | Fixed Maturity AFS Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		2,437	1,730
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		2,340	1,625
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		97	105
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		5,569	5,345
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		5,569	5,345
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		614	593
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		71	67
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		465	451
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		78	75
Trading Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		3,314	1,950
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		45	43
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		3,033	1,840
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		236	67
Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		153	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		67	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		61	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	25
Derivative Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value	[1]	1,498	1,432
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]	826	727
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]	672	705
Other Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		151	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		151	150
Cash And Invested Cash [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		1,593	2,345
Cash And 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		1,593	2,345
GLB Direct Embedded Derivatives [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		439	123
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		439	123
GLB Ceded Embedded Derivatives [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		50	72
GLB Ceded Embedded Derivatives [Member] | Other Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value		(8)
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		50	72
GLB Ceded 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		(8)
Indexed Annuity And IUL Contracts [Member] | Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		872	902
Indexed Annuity And IUL Contracts [Member] | Future Contract Benefits [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value		(1,730)	(1,305)
Indexed Annuity And IUL Contracts [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		872	902
Indexed Annuity And IUL Contracts [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		(1,730)	(1,305)
Separate Account Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets measured at fair value		143,353	132,800
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		696	665
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		142,657	132,135
Reinsurance Related Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities measured at fair value		(177)	(3)
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		(177)	(3)
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]	(759)	(485)
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]	(354)	(314)
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]	$ (405)	$ (171)

[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.