Investments - Securities Available-for-Sale in Gross Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	Sep. 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	$ 1,726	$ 3,592
Gross Unrealized Losses, Less than 12 Months	23	129
Estimated Fair Value, 12 Months or Longer	402	72
Gross Unrealized Losses, 12 Months or Longer	17	6
Total Estimated Fair Value	2,128	3,664
Total Gross Unrealized Losses	40	135
States, Municipalities and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	176	3,251
Gross Unrealized Losses, Less than 12 Months	2	197
Estimated Fair Value, 12 Months or Longer	435	129
Gross Unrealized Losses, 12 Months or Longer	51	75
Total Estimated Fair Value	611	3,380
Total Gross Unrealized Losses	53	272
Residential Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	208	1,293
Gross Unrealized Losses, Less than 12 Months	3	29
Estimated Fair Value, 12 Months or Longer	254	343
Gross Unrealized Losses, 12 Months or Longer	10	63
Total Estimated Fair Value	462	1,636
Total Gross Unrealized Losses	13	92
Commercial Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	506	640
Gross Unrealized Losses, Less than 12 Months	4	22
Estimated Fair Value, 12 Months or Longer	112
Gross Unrealized Losses, 12 Months or Longer	4
Total Estimated Fair Value	618	640
Total Gross Unrealized Losses	8	22
Other Asset-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	507	269
Gross Unrealized Losses, Less than 12 Months	4	3
Estimated Fair Value, 12 Months or Longer	13
Gross Unrealized Losses, 12 Months or Longer	1
Total Estimated Fair Value	520	269
Total Gross Unrealized Losses	5	3
Total Asset-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	1,221	2,202
Gross Unrealized Losses, Less than 12 Months	11	54
Estimated Fair Value, 12 Months or Longer	379	343
Gross Unrealized Losses, 12 Months or Longer	15	63
Total Estimated Fair Value	1,600	2,545
Total Gross Unrealized Losses	26	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		13
Gross Unrealized Losses, Less than 12 Months		1
Estimated Fair Value, 12 Months or Longer	5
Total Estimated Fair Value	5	13
Total Gross Unrealized Losses		1
Foreign Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	35	111
Gross Unrealized Losses, Less than 12 Months		3
Estimated Fair Value, 12 Months or Longer	8
Gross Unrealized Losses, 12 Months or Longer	1
Total Estimated Fair Value	43	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	3,158	9,169
Gross Unrealized Losses, Less than 12 Months	36	384
Estimated Fair Value, 12 Months or Longer	1,229	544
Gross Unrealized Losses, 12 Months or Longer	84	144
Total Estimated Fair Value	4,387	9,713
Total Gross Unrealized Losses	120	528
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	32	87
Gross Unrealized Losses, Less than 12 Months	1	4
Estimated Fair Value, 12 Months or Longer	1
Total Estimated Fair Value	33	87
Total Gross Unrealized Losses	1	4
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	3,190	9,256
Gross Unrealized Losses, Less than 12 Months	37	388
Estimated Fair Value, 12 Months or Longer	1,230	544
Gross Unrealized Losses, 12 Months or Longer	84	144
Total Estimated Fair Value	4,420	9,800
Total Gross Unrealized Losses	$ 121	$ 532