Investments - Securities Available-for-Sale in Gross Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
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
Total Estimated Fair Value	1,361	3,664
Total Gross Unrealized Losses	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
Total Estimated Fair Value	903	3,380
Total Gross Unrealized Losses	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
Total Estimated Fair Value	457	1,636
Total Gross Unrealized Losses	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
Total Estimated Fair Value	376	640
Total Gross Unrealized Losses	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
Total Estimated Fair Value	281	269
Total Gross Unrealized Losses	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
Total Estimated Fair Value	1,114	2,545
Total Gross Unrealized Losses	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
Total Estimated Fair Value	6	13
Total Gross Unrealized Losses	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
Total Estimated Fair Value	48	111
Total Gross Unrealized Losses	1	3
Total Fixed Maturities 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
Total Estimated Fair Value	3,432	9,713
Total Gross Unrealized Losses	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
Total Estimated Fair Value	12	87
Total Gross Unrealized Losses		4
Fixed Maturity Securities [Member]
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
Total Estimated Fair Value	3,444	9,800
Total Gross Unrealized Losses	$ 126	$ 532