Reinsurance - Reinsurance Recoverables (Details) $ in Millions	Dec. 31, 2015 USD ($) Reinsurers	Dec. 31, 2014 USD ($)
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 6,813	$ 7,080
Reserve netted against reinsurance recoverables	$ 3
Minimum [Member] | Standard Poors A Rating Or Better [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	90.00%
Guaranteed Minimum Income Benefit [Member]
Ceded Credit Risk [Line Items]
Number of external reinsurers	3	3
Berkshire Hathway Life Insurance Company Of Nebraska [Member] | Guaranteed Minimum Death Benefits [Member] | Guaranteed Minimum Death Benefit [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 1,123	$ 1,147
Berkshire Hathway Life Insurance Company Of Nebraska [Member] | Guaranteed Minimum Death Benefits [Member] | Guaranteed Minimum Death Benefit [Member] | Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	100.00%
The Lincoln National Life Insurance Company And Lincoln Life And Annuity Of New York [Member] | Individual Life Insurance And Annuity (sold in 1998) [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 3,705	3,817
Prudential Retirement Insurance And Annuity Company [Member] | Retirement Benefits Business (sold in 2004) [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 995	1,092
Prudential Retirement Insurance And Annuity Company [Member] | Retirement Benefits Business (sold in 2004) [Member] | Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	100.00%
Great American Life Insurance Company [Member] | Supplemental Benefits Business (2012 acquistion) [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 315	336
Great American Life Insurance Company [Member] | Supplemental Benefits Business (2012 acquistion) [Member] | Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	99.00%
Other retrocessionaires, including U.S. Government [Member] | Global Health Care, Global Supplemental Benefits, Group Disability and Life [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 553	561
Number of external reinsurers | Reinsurers	75
U.S. Government [Member] | Global Health Care, Global Supplemental Benefits, Group Disability and Life [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 160
Other Retrocessionaires [Member] | Guaranteed Minimum Death Benefits [Member] | Guaranteed Minimum Death Benefit [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 41	39
Other Retrocessionaires [Member] | Guaranteed Minimum Death Benefits [Member] | Guaranteed Minimum Death Benefit [Member] | Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	100.00%
Other Retrocessionaires [Member] | Global Health Care, Global Supplemental Benefits, Group Disability and Life [Member]
Ceded Credit Risk [Line Items]
Maximum reinsurance recoverable from a single reinsurer	$ 88
Other Retrocessionaires [Member] | Global Health Care, Global Supplemental Benefits, Group Disability and Life [Member] | Maximum [Member]
Ceded Credit Risk [Line Items]
Minimum reinsurance recoverable balance from a single reinsurer	$ 1
Other Retrocessionaires [Member] | Global Health Care, Global Supplemental Benefits, Group Disability and Life [Member] | Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	18.00%
Other Retrocessionaires [Member] | Other run-off reinsurance [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 81	$ 88
Other Retrocessionaires [Member] | Other run-off reinsurance [Member] | Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	100.00%