Investments (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available for Sale Securities
Amortized cost	$ 57,971	$ 59,672
Gross unrealized gains	2,397	3,082
Gross unrealized losses	(438)	(314)
Fixed income securities:	59,930	62,440
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	3,827	4,192
Gross unrealized gains	110	139
Gross unrealized losses	(1)	(3)
Fixed income securities:	3,936	4,328
Municipal
Schedule of Available for Sale Securities
Amortized cost	8,111	7,877
Gross unrealized gains	519	645
Gross unrealized losses	(36)	(25)
Fixed income securities:	8,594	8,497
Corporate
Schedule of Available for Sale Securities
Amortized cost	41,153	40,386
Gross unrealized gains	1,524	1,998
Gross unrealized losses	(360)	(240)
Fixed income securities:	42,317	42,144
Foreign government
Schedule of Available for Sale Securities
Amortized cost	1,258	1,543
Gross unrealized gains	67	102
Gross unrealized losses	(1)	0
Fixed income securities:	1,324	1,645
Asset-backed securities (“ABS”)
Schedule of Available for Sale Securities
Amortized cost	2,081	3,971
Gross unrealized gains	21	38
Gross unrealized losses	(26)	(31)
Fixed income securities:	2,076	3,978
Residential mortgage-backed securities (“RMBS”)
Schedule of Available for Sale Securities
Amortized cost	982	1,108
Gross unrealized gains	113	112
Gross unrealized losses	(12)	(13)
Fixed income securities:	1,083	1,207
Commercial mortgage-backed securities (“CMBS”)
Schedule of Available for Sale Securities
Amortized cost	538	573
Gross unrealized gains	39	44
Gross unrealized losses	(2)	(2)
Fixed income securities:	575	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