Guaranteed Benefit Features (Information On Guaranteed Death Benefit Features) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Return of Net Deposits [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Total Account Value	[1]	$ 90,582	$ 87,707
Net Amount At Risk	[1],[2]	$ 348	$ 824
Average attained age of contract holders	[1]	63 years	63 years
Minimum Return [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Total Account Value	[1]	$ 106	$ 105
Net Amount At Risk	[1],[2]	$ 20	$ 22
Average attained age of contract holders	[1]	75 years	75 years
Guaranteed minimum return	[1]	5.00%	5.00%
Anniversary Contract Value [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Total Account Value	[1]	$ 25,359	$ 24,605
Net Amount At Risk	[1],[2]	$ 553	$ 782
Average attained age of contract holders	[1]	70 years	69 years

[1] Our variable contracts with guarantees may offer more than one type of guarantee in each contract; therefore, the amounts listed are not mutually exclusive.

[2] Represents the amount of death benefit in excess of the account balance that is subject to market fluctuations.