Investments (Gross Unrealized Losses Related To AFS And HTM Investments) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Total, Fair Value	$ 880
AFS Investments, Total, Unrealized Losses	(139)
Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Total, Fair Value	355
AFS Investments, Total, Unrealized Losses	(23)
Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Total, Fair Value	235
AFS Investments, Total, Unrealized Losses	(90)
HTM Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
HTM Investments, Less than 12 Months, Fair Value	297	284
HTM Investments, Less than 12 Months, Unrealized Losses	(19)	(31)
HTM Investments, 12 Months or Longer, Fair Value	1,287	2,185
HTM Investments, 12 Months or Longer, Unrealized Losses	(138)	(340)
HTM Investments, Total, Fair Value	1,584	2,469
HTM Investments, Total, Unrealized Losses	(157)	(371)
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	297	284
HTM Investments, Less than 12 Months, Unrealized Losses	(19)	(31)
HTM Investments, 12 Months or Longer, Fair Value	1,287	2,185
HTM Investments, 12 Months or Longer, Unrealized Losses	(138)	(340)
HTM Investments, Total, Fair Value	1,584	2,469
HTM Investments, Total, Unrealized Losses	(157)	(371)
AFS Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value	702	912
AFS Investments, Less than 12 Months, Unrealized Losses	(4)	(36)
AFS Investments, 12 Months or Longer, Fair Value	582	1,475
AFS Investments, 12 Months or Longer, Unrealized Losses	(148)	(442)
AFS Investments, Total, Fair Value	1,284	2,387
AFS Investments, Total, Unrealized Losses	(152)	(478)
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	701	820
AFS Investments, Less than 12 Months, Unrealized Losses	(4)	(33)
AFS Investments, 12 Months or Longer, Fair Value	383	1,252
AFS Investments, 12 Months or Longer, Unrealized Losses	(124)	(385)
AFS Investments, Total, Fair Value	1,084	2,072
AFS Investments, Total, Unrealized Losses	(128)	(418)
AFS Investments [Member] | 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	47
AFS Investments, Less than 12 Months, Unrealized Losses		(3)
AFS Investments, 12 Months or Longer, Fair Value	1	45
AFS Investments, 12 Months or Longer, Unrealized Losses		(16)
AFS Investments, Total, Fair Value	2	92
AFS Investments, Total, Unrealized Losses		(19)
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	202	297
AFS Investments, Less than 12 Months, Unrealized Losses	(2)	(15)
AFS Investments, 12 Months or Longer, Fair Value	57	418
AFS Investments, 12 Months or Longer, Unrealized Losses	(18)	(91)
AFS Investments, Total, Fair Value	259	715
AFS Investments, Total, Unrealized Losses	(20)	(106)
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	234	200
AFS Investments, Less than 12 Months, Unrealized Losses	(1)
AFS Investments, Total, Fair Value	234	200
AFS Investments, Total, Unrealized Losses	(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	69	166
AFS Investments, Less than 12 Months, Unrealized Losses		(2)
AFS Investments, 12 Months or Longer, Fair Value	87	151
AFS Investments, 12 Months or Longer, Unrealized Losses	(12)	(17)
AFS Investments, Total, Fair Value	156	317
AFS Investments, Total, Unrealized Losses	(12)	(19)
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	11	20
AFS Investments, 12 Months or Longer, Fair Value	1
AFS Investments, Total, Fair Value	12	20
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	173	20
AFS Investments, Less than 12 Months, Unrealized Losses	(1)
AFS Investments, 12 Months or Longer, Fair Value	38	49
AFS Investments, Total, Fair Value	211	69
AFS Investments, Total, Unrealized Losses	(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	4	34
AFS Investments, Less than 12 Months, Unrealized Losses		(5)
AFS Investments, 12 Months or Longer, Fair Value	28	167
AFS Investments, 12 Months or Longer, Unrealized Losses	(8)	(78)
AFS Investments, Total, Fair Value	32	201
AFS Investments, Total, Unrealized Losses	(8)	(83)
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	17
AFS Investments, Less than 12 Months, Unrealized Losses		(2)
AFS Investments, 12 Months or Longer, Fair Value	27	22
AFS Investments, 12 Months or Longer, Unrealized Losses	(4)	(8)
AFS Investments, Total, Fair Value	30	39
AFS Investments, Total, Unrealized Losses	(4)	(10)
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	1	13
AFS Investments, Less than 12 Months, Unrealized Losses		(2)
AFS Investments, 12 Months or Longer, Fair Value	80	117
AFS Investments, 12 Months or Longer, Unrealized Losses	(71)	(116)
AFS Investments, Total, Fair Value	81	130
AFS Investments, Total, Unrealized Losses	(71)	(118)
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	4	53
AFS Investments, Less than 12 Months, Unrealized Losses		(7)
AFS Investments, 12 Months or Longer, Fair Value	65	328
AFS Investments, 12 Months or Longer, Unrealized Losses	(11)	(75)
AFS Investments, Total, Fair Value	69	381
AFS Investments, Total, Unrealized Losses	(11)	(82)
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		2
AFS Investments, 12 Months or Longer, Fair Value	31
AFS Investments, 12 Months or Longer, Unrealized Losses	(6)
AFS Investments, Total, Fair Value	31	2
AFS Investments, Total, Unrealized Losses	(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	82	90
AFS Investments, 12 Months or Longer, Unrealized Losses	(10)	(26)
AFS Investments, Total, Fair Value	82	93
AFS Investments, Total, Unrealized Losses	(10)	(26)
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, Less than 12 Months, Fair Value		9
AFS Investments, 12 Months or Longer, Fair Value	85	88
AFS Investments, 12 Months or Longer, Unrealized Losses	(8)	(15)
AFS Investments, Total, Fair Value	85	97
AFS Investments, Total, Unrealized Losses	(8)	(15)
AFS Investments [Member] | Variable Interest Entity [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
AFS Investments, Less than 12 Months, Fair Value		31
AFS Investments, Total, Fair Value		$ 31