Life Policy And Investment Contract Reservess (Reserve In Addition To The Account Balance Based On Expected No-Lapse Guarantee Benefits And Expected Policy Assessments) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	$ 2,671	$ 2,583
Life Policy Reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	1,056	987
Life Policy Reserves | Ordinary/Traditional Life
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	1,011	943
Life Policy Reserves | Other Life Policy Reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	45	44
Investment contract reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	1,615	1,596
Investment contract reserves | Deferred Annuities
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	861	860
Investment contract reserves | Universal Life
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	578	558
Investment contract reserves | Structured Settlements
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	170	174
Investment contract reserves | Other Investment Contract Reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	$ 6	$ 4