Derivative Financial Instruments (Summary of aggregate contractual or notional amounts and gross estimated fair values related to derivative financial instruments) (Details) (Not Designated as Hedging Instrument [Member], Equity warrants [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Not Designated as Hedging Instrument [Member] | Equity warrants [Member]
Derivative [Line Items]
Contractual/notional amount	$ 5	$ 5
Estimated fair value asset
Estimated fair value (liability)