Investments (Securities in a gross unrealized loss position) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	$ 1,779	$ 9,256
Gross Unrealized Losses, Less than 12 Months	22	388
Estimated Fair Value, 12 Months or Longer	1,665	544
Gross Unrealized Losses, 12 Months or Longer	104	144
Estimated Fair Value, Total	3,444	9,800
Gross Unrealized Losses, Total	126	532
Corporate and other bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	813	3,592
Gross Unrealized Losses, Less than 12 Months	12	129
Estimated Fair Value, 12 Months or Longer	548	72
Gross Unrealized Losses, 12 Months or Longer	18	6
Estimated Fair Value, Total	1,361	3,664
Gross Unrealized Losses, Total	30	135
States, municipalities and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	316	3,251
Gross Unrealized Losses, Less than 12 Months	2	197
Estimated Fair Value, 12 Months or Longer	587	129
Gross Unrealized Losses, 12 Months or Longer	68	75
Estimated Fair Value, Total	903	3,380
Gross Unrealized Losses, Total	70	272
Residential mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	125	1,293
Gross Unrealized Losses, Less than 12 Months	1	29
Estimated Fair Value, 12 Months or Longer	332	343
Gross Unrealized Losses, 12 Months or Longer	13	63
Estimated Fair Value, Total	457	1,636
Gross Unrealized Losses, Total	14	92
Commercial mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	205	640
Gross Unrealized Losses, Less than 12 Months	2	22
Estimated Fair Value, 12 Months or Longer	171
Gross Unrealized Losses, 12 Months or Longer	5
Estimated Fair Value, Total	376	640
Gross Unrealized Losses, Total	7	22
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	269	269
Gross Unrealized Losses, Less than 12 Months	3	3
Estimated Fair Value, 12 Months or Longer	12
Gross Unrealized Losses, 12 Months or Longer
Estimated Fair Value, Total	281	269
Gross Unrealized Losses, Total	3	3
Total asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	599	2,202
Gross Unrealized Losses, Less than 12 Months	6	54
Estimated Fair Value, 12 Months or Longer	515	343
Gross Unrealized Losses, 12 Months or Longer	18	63
Estimated Fair Value, Total	1,114	2,545
Gross Unrealized Losses, Total	24	117
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	2	13
Gross Unrealized Losses, Less than 12 Months	1	1
Estimated Fair Value, 12 Months or Longer	4
Gross Unrealized Losses, 12 Months or Longer
Estimated Fair Value, Total	6	13
Gross Unrealized Losses, Total	1	1
Foreign Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	39	111
Gross Unrealized Losses, Less than 12 Months	1	3
Estimated Fair Value, 12 Months or Longer	9
Gross Unrealized Losses, 12 Months or Longer
Estimated Fair Value, Total	48	111
Gross Unrealized Losses, Total	1	3
Total fixed maturity securities available-for-sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	1,769	9,169
Gross Unrealized Losses, Less than 12 Months	22	384
Estimated Fair Value, 12 Months or Longer	1,663	544
Gross Unrealized Losses, 12 Months or Longer	104	144
Estimated Fair Value, Total	3,432	9,713
Gross Unrealized Losses, Total	126	528
Preferred stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	10	87
Gross Unrealized Losses, Less than 12 Months		4
Estimated Fair Value, 12 Months or Longer	2
Gross Unrealized Losses, 12 Months or Longer
Estimated Fair Value, Total	12	87
Gross Unrealized Losses, Total		$ 4