Investments (Summary of fixed maturity and equity securities) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Cost or Amortized Cost	$ 37,707	$ 39,490
Gross Unrealized Gains	3,325	2,460
Gross Unrealized Losses	121	532
Estimated fair value	40,911	41,418
Corporate and other bonds [Member]
Cost or Amortized Cost	17,480	19,352
Gross Unrealized Gains	1,704	1,645
Gross Unrealized Losses	40	135
Estimated fair value	19,144	20,862
Unrealized OTTI Losses (Gains)
States, municipalities and political subdivisions [Member]
Cost or Amortized Cost	11,217	11,281
Gross Unrealized Gains	1,295	548
Gross Unrealized Losses	53	272
Estimated fair value	12,459	11,557
Unrealized OTTI Losses (Gains)
Residential mortgage-backed [Member]
Cost or Amortized Cost	4,972	4,940
Gross Unrealized Gains	187	123
Gross Unrealized Losses	13	92
Estimated fair value	5,146	4,971
Unrealized OTTI Losses (Gains)	(54)	(37)
Commercial mortgage-backed [Member]
Cost or Amortized Cost	2,079	1,995
Gross Unrealized Gains	87	90
Gross Unrealized Losses	8	22
Estimated fair value	2,158	2,063
Unrealized OTTI Losses (Gains)	(2)	(3)
Other asset-backed [Member]
Cost or Amortized Cost	1,222	945
Gross Unrealized Gains	13	13
Gross Unrealized Losses	5	3
Estimated fair value	1,230	955
Unrealized OTTI Losses (Gains)
Total asset-backed [Member]
Cost or Amortized Cost	8,273	7,880
Gross Unrealized Gains	287	226
Gross Unrealized Losses	26	117
Estimated fair value	8,534	7,989
Unrealized OTTI Losses (Gains)	(56)	(40)
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Cost or Amortized Cost	25	139
Gross Unrealized Gains	5	6
Gross Unrealized Losses		1
Estimated fair value	30	144
Unrealized OTTI Losses (Gains)
Foreign Government [Member]
Cost or Amortized Cost	456	531
Gross Unrealized Gains	16	15
Gross Unrealized Losses	1	3
Estimated fair value	471	543
Unrealized OTTI Losses (Gains)
Redeemable preferred stock [Member]
Cost or Amortized Cost	39	92
Gross Unrealized Gains	3	10
Gross Unrealized Losses
Estimated fair value	42	102
Unrealized OTTI Losses (Gains)
Total fixed maturity securities available-for-sale [Member]
Cost or Amortized Cost	37,490	39,275
Gross Unrealized Gains	3,310	2,450
Gross Unrealized Losses	120	528
Estimated fair value	40,680	41,197
Unrealized OTTI Losses (Gains)	(56)	(40)
Total fixed maturity securities trading [Member]
Cost or Amortized Cost, Trading Securities	20	36
Estimated Fair Value, Trading Securities	20	36
Common stock [Member]
Cost or Amortized Cost	35	36
Gross Unrealized Gains	11	9
Gross Unrealized Losses
Estimated fair value	46	45
Preferred stock [Member]
Cost or Amortized Cost	162	143
Gross Unrealized Gains	4	1
Gross Unrealized Losses	1	4
Estimated fair value	165	140
Total equity securities available-for-sale [Member]
Cost or Amortized Cost	197	179
Gross Unrealized Gains	15	10
Gross Unrealized Losses	1	4
Estimated fair value	$ 211	$ 185