Derivatives (Details 8) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Credit Derivatives [Line Items]
Estimated Fair Value of Derivatives in Net Liability Position	$ 850	$ 475
Estimated Fair Value Of Incremental Collateral Provided Upon A One Notch Downgrade In The Company's Credit Rating	35	48
Estimated Fair Value Of Incremental Collateral Provided Upon A Downgrade In The Company's Credit Rating to a Level that Triggers Full Overnight Collateralization or Termination of the Derivative Position	73	104
Fixed Maturities [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Collateral Provided	875	416
Cash [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Collateral Provided	1	8
Derivatives Subject To Credit-Contingent Provisions [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Derivatives in Net Liability Position	771	447
Estimated Fair Value Of Incremental Collateral Provided Upon A One Notch Downgrade In The Company's Credit Rating	35	48
Estimated Fair Value Of Incremental Collateral Provided Upon A Downgrade In The Company's Credit Rating to a Level that Triggers Full Overnight Collateralization or Termination of the Derivative Position	73	104
Derivatives Subject To Credit-Contingent Provisions [Member] | Fixed Maturities [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Collateral Provided	775	405
Derivatives Subject To Credit-Contingent Provisions [Member] | Cash [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Collateral Provided	0	4
Derivatives Not Subject To Credit-Contingent Provisions [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Derivatives in Net Liability Position	79	28
Estimated Fair Value Of Incremental Collateral Provided Upon A One Notch Downgrade In The Company's Credit Rating	0	0
Estimated Fair Value Of Incremental Collateral Provided Upon A Downgrade In The Company's Credit Rating to a Level that Triggers Full Overnight Collateralization or Termination of the Derivative Position	0	0
Derivatives Not Subject To Credit-Contingent Provisions [Member] | Fixed Maturities [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Collateral Provided	100	11
Derivatives Not Subject To Credit-Contingent Provisions [Member] | Cash [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Collateral Provided	$ 1	$ 4