Investments (Summary of fixed maturity and equity securities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Cost or Amortized Cost	$ 39,490	$ 38,398
Gross Unrealized Gains	2,460	4,639
Gross Unrealized Losses	532	155
Estimated fair value	41,418	42,882
Corporate and other bonds [Member]
Cost or Amortized Cost	19,352	19,530
Gross Unrealized Gains	1,645	2,698
Gross Unrealized Losses	135	21
Estimated fair value	20,862	22,207
Unrealized OTTI Losses (Gains)
States, municipalities and political subdivisions [Member]
Cost or Amortized Cost	11,281	9,372
Gross Unrealized Gains	548	1,455
Gross Unrealized Losses	272	44
Estimated fair value	11,557	10,783
Unrealized OTTI Losses (Gains)
Residential mortgage-backed [Member]
Cost or Amortized Cost	4,940	5,745
Gross Unrealized Gains	123	246
Gross Unrealized Losses	92	71
Estimated fair value	4,971	5,920
Unrealized OTTI Losses (Gains)	(37)	(28)
Commercial mortgage-backed [Member]
Cost or Amortized Cost	1,995	1,692
Gross Unrealized Gains	90	147
Gross Unrealized Losses	22	17
Estimated fair value	2,063	1,822
Unrealized OTTI Losses (Gains)	(3)	(3)
Other asset-backed [Member]
Cost or Amortized Cost	945	929
Gross Unrealized Gains	13	23
Gross Unrealized Losses	3
Estimated fair value	955	952
Unrealized OTTI Losses (Gains)
Total asset-backed [Member]
Cost or Amortized Cost	7,880	8,366
Gross Unrealized Gains	226	416
Gross Unrealized Losses	117	88
Estimated fair value	7,989	8,694
Unrealized OTTI Losses (Gains)	(40)	(31)
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Cost or Amortized Cost	139	172
Gross Unrealized Gains	6	11
Gross Unrealized Losses	1	1
Estimated fair value	144	182
Unrealized OTTI Losses (Gains)
Foreign Government Debt Securities [Member]
Cost or Amortized Cost	531	588
Gross Unrealized Gains	15	25
Gross Unrealized Losses	3
Estimated fair value	543	613
Unrealized OTTI Losses (Gains)
Redeemable preferred stock [Member]
Cost or Amortized Cost	92	113
Gross Unrealized Gains	10	13
Gross Unrealized Losses		1
Estimated fair value	102	125
Unrealized OTTI Losses (Gains)
Total fixed maturity securities available-for-sale [Member]
Cost or Amortized Cost	39,275	38,141
Gross Unrealized Gains	2,450	4,618
Gross Unrealized Losses	528	155
Estimated fair value	41,197	42,604
Unrealized OTTI Losses (Gains)	(40)	(31)
Total fixed maturity securities trading [Member]
Cost or Amortized Cost, Trading Securities	36	29
Gross Unrealized Gains, Trading Securities
Gross Unrealized Losses, Trading Securities
Estimated Fair Value, Trading Securities	36	29
Common stock [Member]
Cost or Amortized Cost	36	38
Gross Unrealized Gains	9	14
Gross Unrealized Losses
Estimated fair value	45	52
Preferred stock [Member]
Cost or Amortized Cost	143	190
Gross Unrealized Gains	1	7
Gross Unrealized Losses	4
Estimated fair value	140	197
Total equity securities available-for-sale [Member]
Cost or Amortized Cost	179	228
Gross Unrealized Gains	10	21
Gross Unrealized Losses	4
Estimated fair value	$ 185	$ 249