Fair Value Fair Value (Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Other Credit Derivatives [Member] | Asset-Backed Securities [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Investments, Fair Value Disclosure		$ 24
Fair Value, Inputs, Level 3 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Investments, Fair Value Disclosure	$ 0	$ 0