Investments (Summary of fixed maturity and equity securities) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Cost or Amortized Cost	$ 37,387	$ 39,490
Gross Unrealized Gains	3,401	2,460
Gross Unrealized Losses	126	532
Estimated fair value	40,662	41,418
Corporate and other bonds [Member]
Cost or Amortized Cost	17,276	19,352
Gross Unrealized Gains	1,852	1,645
Gross Unrealized Losses	30	135
Estimated fair value	19,098	20,862
Unrealized OTTI Losses (Gains)
States, municipalities and political subdivisions [Member]
Cost or Amortized Cost	11,215	11,281
Gross Unrealized Gains	1,178	548
Gross Unrealized Losses	70	272
Estimated fair value	12,323	11,557
Unrealized OTTI Losses (Gains)
Residential mortgage-backed [Member]
Cost or Amortized Cost	4,882	4,940
Gross Unrealized Gains	202	123
Gross Unrealized Losses	14	92
Estimated fair value	5,070	4,971
Unrealized OTTI Losses (Gains)	(51)	(37)
Commercial mortgage-backed [Member]
Cost or Amortized Cost	1,999	1,995
Gross Unrealized Gains	107	90
Gross Unrealized Losses	7	22
Estimated fair value	2,099	2,063
Unrealized OTTI Losses (Gains)	(3)	(3)
Other asset-backed [Member]
Cost or Amortized Cost	1,172	945
Gross Unrealized Gains	16	13
Gross Unrealized Losses	3	3
Estimated fair value	1,185	955
Unrealized OTTI Losses (Gains)
Total asset-backed [Member]
Cost or Amortized Cost	8,053	7,880
Gross Unrealized Gains	325	226
Gross Unrealized Losses	24	117
Estimated fair value	8,354	7,989
Unrealized OTTI Losses (Gains)	(54)	(40)
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Cost or Amortized Cost	61	139
Gross Unrealized Gains	6	6
Gross Unrealized Losses	1	1
Estimated fair value	66	144
Unrealized OTTI Losses (Gains)
Foreign Government [Member]
Cost or Amortized Cost	533	531
Gross Unrealized Gains	18	15
Gross Unrealized Losses	1	3
Estimated fair value	550	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	37,177	39,275
Gross Unrealized Gains	3,382	2,450
Gross Unrealized Losses	126	528
Estimated fair value	40,433	41,197
Unrealized OTTI Losses (Gains)	(54)	(40)
Total fixed maturity securities trading [Member]
Cost or Amortized Cost, Trading Securities	35	36
Gross Unrealized Gains, Trading Securities
Gross Unrealized Losses, Trading Securities
Estimated Fair Value, Trading Securities	35	36
Common stock [Member]
Cost or Amortized Cost	46	36
Gross Unrealized Gains	14	9
Gross Unrealized Losses
Estimated fair value	60	45
Preferred stock [Member]
Cost or Amortized Cost	129	143
Gross Unrealized Gains	5	1
Gross Unrealized Losses		4
Estimated fair value	134	140
Total equity securities available-for-sale [Member]
Cost or Amortized Cost	175	179
Gross Unrealized Gains	19	10
Gross Unrealized Losses		4
Estimated fair value	$ 194	$ 185