Investments (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available for Sale Securities
Amortized cost	$ 56,918	$ 59,672
Gross unrealized gains	2,097	3,082
Gross unrealized losses	(758)	(314)
Fixed income securities:	58,257	62,440
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	3,642	4,192
Gross unrealized gains	118	139
Gross unrealized losses	0	(3)
Fixed income securities:	3,760	4,328
Municipal
Schedule of Available for Sale Securities
Amortized cost	7,082	7,877
Gross unrealized gains	431	645
Gross unrealized losses	(19)	(25)
Fixed income securities:	7,494	8,497
Corporate
Schedule of Available for Sale Securities
Amortized cost	40,997	40,386
Gross unrealized gains	1,322	1,998
Gross unrealized losses	(690)	(240)
Fixed income securities:	41,629	42,144
Foreign government
Schedule of Available for Sale Securities
Amortized cost	1,026	1,543
Gross unrealized gains	60	102
Gross unrealized losses	(1)	0
Fixed income securities:	1,085	1,645
Asset-backed securities (“ABS”)
Schedule of Available for Sale Securities
Amortized cost	2,727	3,971
Gross unrealized gains	19	38
Gross unrealized losses	(35)	(31)
Fixed income securities:	2,711	3,978
Residential mortgage-backed securities (“RMBS”)
Schedule of Available for Sale Securities
Amortized cost	913	1,108
Gross unrealized gains	108	112
Gross unrealized losses	(10)	(13)
Fixed income securities:	1,011	1,207
Commercial mortgage-backed securities (“CMBS”)
Schedule of Available for Sale Securities
Amortized cost	510	573
Gross unrealized gains	35	44
Gross unrealized losses	(3)	(2)
Fixed income securities:	542	615
Redeemable preferred stock
Schedule of Available for Sale Securities
Amortized cost	21	22
Gross unrealized gains	4	4
Gross unrealized losses	0	0
Fixed income securities:	$ 25	$ 26