Derivative Instruments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Jul. 31, 2014
Derivative [Line Items]
Net derivative gains to be reclassified into earnings within the next 12 months	$ 19	$ 19
Derivative asset offset against collateral	22	22
Derivative liability offset against collateral	22	22
Net derivative assets	40	40
Net derivative liabilities	10	10
Interest Rate Swap | Fair Value Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Derivative liability	2,400	2,400	$ 2,400
Foreign Exchange Contract | Not Designated as Hedging Instrument | Interest and Other, Net | Future
Derivative [Line Items]
Net derivative gains	8	8
Net derivative losses	$ 8	$ 8