Investments - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	$ 1,190	$ 1,196	$ 1,206
Less: investment expenses	43	43	40
Net investment income	1,147	1,153	1,166
Carrying Value Of Non Income Producing Real Estate Entities And Securities Partnerships	220	277
Net investment income for separate accounts	236	262	225
Fixed Maturities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	899	879	876
Equity securities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	4	3	3
Commercial Mortgage Loans [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	91	112	133
Policy Loans [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	72	72	72
Other Long Term Investments [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	98	116	105
Short-term investments and cash [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	$ 26	$ 14	$ 17