Investment Income and Gains and Losses - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	$ 1,196	$ 1,206	$ 1,200
Less: investment expenses	43	40	36
Net investment income	1,153	1,166	1,164
Net investment income for separate accounts	262	225	232
Fixed Maturities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	879	876	823
Equity securities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	3	3	6
Commercial Mortgage Loans [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	112	133	174
Policy Loans [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	72	72	74
Other Long Term Investments [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	116	105	101
Short-term investments and cash [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	$ 14	$ 17	$ 22