Investments (Gross Unrealized Losses Related To AFS And HTM Investments) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Total, Fair Value	$ 1,130
AFS Investments, Total, Unrealized Losses	(126)
Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Total, Fair Value	551
AFS Investments, Total, Unrealized Losses	(18)
Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Total, Fair Value	227
AFS Investments, Total, Unrealized Losses	(82)
HTM Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
HTM Investments, Less than 12 Months, Fair Value	311	297
HTM Investments, Less than 12 Months, Unrealized Losses	(4)	(19)
HTM Investments, 12 Months or Longer, Fair Value	1,336	1,287
HTM Investments, 12 Months or Longer, Unrealized Losses	(89)	(138)
HTM Investments, Total, Fair Value	1,647	1,584
HTM Investments, Total, Unrealized Losses	(93)	(157)
HTM Investments [Member] | Variable Interest Entity [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
HTM Investments, Less than 12 Months, Fair Value	311	297
HTM Investments, Less than 12 Months, Unrealized Losses	(4)	(19)
HTM Investments, 12 Months or Longer, Fair Value	1,336	1,287
HTM Investments, 12 Months or Longer, Unrealized Losses	(89)	(138)
HTM Investments, Total, Fair Value	1,647	1,584
HTM Investments, Total, Unrealized Losses	(93)	(157)
AFS Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	994	702
AFS Investments, Less than 12 Months, Unrealized Losses	(11)	(4)
AFS Investments, 12 Months or Longer, Fair Value	520	582
AFS Investments, 12 Months or Longer, Unrealized Losses	(124)	(148)
AFS Investments, Total, Fair Value	1,514	1,284
AFS Investments, Total, Unrealized Losses	(135)	(152)
AFS Investments [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	980	701
AFS Investments, Less than 12 Months, Unrealized Losses	(11)	(4)
AFS Investments, 12 Months or Longer, Fair Value	340	383
AFS Investments, 12 Months or Longer, Unrealized Losses	(105)	(124)
AFS Investments, Total, Fair Value	1,320	1,084
AFS Investments, Total, Unrealized Losses	(116)	(128)
AFS Investments [Member] | Corporate Obligations [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	267	202
AFS Investments, Less than 12 Months, Unrealized Losses	(5)	(2)
AFS Investments, 12 Months or Longer, Fair Value	54	57
AFS Investments, 12 Months or Longer, Unrealized Losses	(15)	(18)
AFS Investments, Total, Fair Value	321	259
AFS Investments, Total, Unrealized Losses	(20)	(20)
AFS Investments [Member] | U.S. Treasury And Government Agency [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	70	234
AFS Investments, Less than 12 Months, Unrealized Losses	(1)	(1)
AFS Investments, Total, Fair Value	70	234
AFS Investments, Total, Unrealized Losses	(1)	(1)
AFS Investments [Member] | State And Municipal Bonds [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	196	69
AFS Investments, Less than 12 Months, Unrealized Losses	(2)
AFS Investments, 12 Months or Longer, Fair Value	85	87
AFS Investments, 12 Months or Longer, Unrealized Losses	(6)	(12)
AFS Investments, Total, Fair Value	281	156
AFS Investments, Total, Unrealized Losses	(8)	(12)
AFS Investments [Member] | Foreign Governments [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	32	11
AFS Investments, 12 Months or Longer, Fair Value		1
AFS Investments, Total, Fair Value	32	12
AFS Investments [Member] | Residential Mortgage-Backed Agency [Member] | Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	403	173
AFS Investments, Less than 12 Months, Unrealized Losses	(3)	(1)
AFS Investments, 12 Months or Longer, Fair Value	36	38
AFS Investments, Total, Fair Value	439	211
AFS Investments, Total, Unrealized Losses	(3)	(1)
AFS Investments [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	2	4
AFS Investments, 12 Months or Longer, Fair Value	27	28
AFS Investments, 12 Months or Longer, Unrealized Losses	(7)	(8)
AFS Investments, Total, Fair Value	29	32
AFS Investments, Total, Unrealized Losses	(7)	(8)
AFS Investments [Member] | Commercial Mortgage-Backed [Member] | Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	3	3
AFS Investments, 12 Months or Longer, Fair Value	1	27
AFS Investments, 12 Months or Longer, Unrealized Losses	(1)	(4)
AFS Investments, Total, Fair Value	4	30
AFS Investments, Total, Unrealized Losses	(1)	(4)
AFS Investments [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	4	1
AFS Investments, 12 Months or Longer, Fair Value	74	80
AFS Investments, 12 Months or Longer, Unrealized Losses	(65)	(71)
AFS Investments, Total, Fair Value	78	81
AFS Investments, Total, Unrealized Losses	(65)	(71)
AFS Investments [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	3	4
AFS Investments, 12 Months or Longer, Fair Value	63	65
AFS Investments, 12 Months or Longer, Unrealized Losses	(11)	(11)
AFS Investments, Total, Fair Value	66	69
AFS Investments, Total, Unrealized Losses	(11)	(11)
AFS Investments [Member] | Perpetual debt and equity securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	1	1
AFS Investments, 12 Months or Longer, Fair Value		1
AFS Investments, Total, Fair Value	1	2
AFS Investments [Member] | Variable Interest Entity [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	10
AFS Investments, 12 Months or Longer, Fair Value	21	31
AFS Investments, 12 Months or Longer, Unrealized Losses	(6)	(6)
AFS Investments, Total, Fair Value	31	31
AFS Investments, Total, Unrealized Losses	(6)	(6)
AFS Investments [Member] | Variable Interest Entity [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	3
AFS Investments, 12 Months or Longer, Fair Value	76	82
AFS Investments, 12 Months or Longer, Unrealized Losses	(7)	(10)
AFS Investments, Total, Fair Value	79	82
AFS Investments, Total, Unrealized Losses	(7)	(10)
AFS Investments [Member] | Variable Interest Entity [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, 12 Months or Longer, Fair Value	83	85
AFS Investments, 12 Months or Longer, Unrealized Losses	(6)	(8)
AFS Investments, Total, Fair Value	83	85
AFS Investments, Total, Unrealized Losses	$ (6)	$ (8)