Derivative Instruments (Open Credit Default Swap Liabilities) (Details) - Open Credit Default Swap Liabilities [Member] $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($) item
Summary Of Credit Derivatives
Number of instruments | item		1	2
Fair value	[1]	$ 1
Maximum potential payout		$ 56	$ 40
3/20/2017 maturity
Summary Of Credit Derivatives
Credit rating of underlying obligation	[2]		BBB+
Number of instruments | item			2
Maximum potential payout			$ 40
6/20/2022 maturity
Summary Of Credit Derivatives
Credit rating of underlying obligation	[2]	BBB+
Number of instruments | item		1
Fair value	[1]	$ 1
Maximum potential payout		$ 56

[1] Broker quotes are used to determine the market value of our credit default swaps.Credit default swaps were entered into in order to hedge the liability exposure on certain variable annuity products.Sellers do not have the right to demand indemnification or compensation from third parties in case of a loss (payment) on the contract.

[2] Represents average credit ratings based on the midpoint of the applicable ratings among Moody’s, S&P and Fitch Ratings, as scaled to the corresponding S&P ratings.