Fair Value Measurements - Assets and liabilities measured and carried at fair value in the financial statements (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Assets:
Available for sale (AFS) fixed maturities		$ 37,818	$ 34,544
Trading fixed maturities		350	359
Assets of managed investment entities (“MIE”)		4,767	4,765
Variable annuity assets (separate accounts)	[1]	628	600
Derivatives included in other investments and other assets		629	492
Total assets accounted for at fair value		45,832	42,319
Liabilities:
Liabilities of managed investment entities		4,506	4,549
Total liabilities accounted for at fair value		6,830	6,337
Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		2,293	1,759
Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	(1)
Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		31	30
Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		37,818	34,544
Trading fixed maturities		350	359
U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		257	315
States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		6,997	6,781
Foreign government
Assets:
Available for sale (AFS) fixed maturities		144	136
Residential MBS
Assets:
Available for sale (AFS) fixed maturities		3,396	3,635
Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		1,010	1,493
Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		7,396	5,959
Corporate and other
Assets:
Available for sale (AFS) fixed maturities		18,618	16,225
Equity securities
Assets:
Equity securities — AFS and trading		1,639	1,558
Other assets — derivatives
Assets:
Derivatives included in other investments and other assets		1	1
Level 1
Assets:
Assets of managed investment entities (“MIE”)		368	380
Variable annuity assets (separate accounts)	[1]	0	0
Total assets accounted for at fair value		1,963	1,877
Liabilities:
Liabilities of managed investment entities		348	363
Total liabilities accounted for at fair value		348	363
Level 1 | Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 1 | Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 1 | Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 1 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		150	162
Trading fixed maturities		48	30
Level 1 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		120	133
Level 1 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		30	29
Level 1 | Equity securities
Assets:
Equity securities — AFS and trading		1,397	1,305
Level 1 | Other assets — derivatives
Assets:
Derivatives included in other investments and other assets		0	0
Level 2
Assets:
Assets of managed investment entities (“MIE”)		4,378	4,356
Variable annuity assets (separate accounts)	[1]	628	600
Total assets accounted for at fair value		41,759	38,680
Liabilities:
Liabilities of managed investment entities		4,138	4,158
Total liabilities accounted for at fair value		4,169	4,187
Level 2 | Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 2 | Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	(1)
Level 2 | Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		31	30
Level 2 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		35,742	32,823
Trading fixed maturities		302	329
Level 2 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		129	174
Level 2 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		6,845	6,641
Level 2 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		144	136
Level 2 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		3,252	3,445
Level 2 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		974	1,468
Level 2 | Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		6,860	5,475
Level 2 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		17,538	15,484
Level 2 | Equity securities
Assets:
Equity securities — AFS and trading		79	79
Level 2 | Other assets — derivatives
Assets:
Derivatives included in other investments and other assets		1	1
Level 3
Assets:
Assets of managed investment entities (“MIE”)		21	29
Variable annuity assets (separate accounts)	[1]	0	0
Total assets accounted for at fair value		2,110	1,762
Liabilities:
Liabilities of managed investment entities		20	28
Total liabilities accounted for at fair value		2,313	1,787
Level 3 | Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		2,293	1,759
Level 3 | Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 3 | Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 3 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		1,926	1,559
Trading fixed maturities		0	0
Level 3 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		8	8
Level 3 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		152	140
Level 3 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 3 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		144	190
Level 3 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		36	25
Level 3 | Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		536	484
Level 3 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		1,050	712
Level 3 | Equity securities
Assets:
Equity securities — AFS and trading		163	174
Level 3 | Other assets — derivatives
Assets:
Derivatives included in other investments and other assets		0	0
Equity index call options | Equity index call options
Assets:
Derivatives included in other investments and other assets		629	492
Equity index call options | Level 1 | Equity index call options
Assets:
Derivatives included in other investments and other assets		0	0
Equity index call options | Level 2 | Equity index call options
Assets:
Derivatives included in other investments and other assets		629	492
Equity index call options | Level 3 | Equity index call options
Assets:
Derivatives included in other investments and other assets		$ 0	$ 0

[1] Variable annuity liabilities equal the fair value of variable annuity assets.