Derivatives and Hedging Activities (Schedule of Interest Rate Derivative Activity (Details) - Interest Rate Swap [Member] - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount of Derivative Instrument, Undesignated	$ 0	$ 0	$ 38	$ 0	$ 0	$ 0	$ 0	$ 0	$ 38	$ 0
Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Notional Amount of Derivative Instrument, Issued	0	0	0	0	0	0	0	55	0	55
Notional Amount of Derivative Instrument, Terminated	$ 0	$ 0	$ 175	$ 0	$ 0	$ 0	$ 0	$ 0	$ 175	$ 0