Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ 3
Maximum length of time hedged in cash flow hedge	19 years
Credit Protection Purchased Notional Amounts	$ 7	$ 7
Credit Derivative Protection Purchased Fair Value Asset (Liability) (less than)	$ (1)	$ 1