Derivatives and Hedging - Schedule of amounts of derivative gains (losses) recognized in the Consolidated Financial Statements (Details) (Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flow Hedging [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	$ (2)	$ (2)	$ (21)
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(15)	(11)	(35)
Cash Flow Hedging [Member] | Compensation and Benefits [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	11	(17)	(8)
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(5)	(12)	(9)
Cash Flow Hedging [Member] | Other General Expenses [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(3)	0	(19)
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	3	(9)	(16)
Cash Flow Hedging [Member] | Interest Expense [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	2	0
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(11)	(4)	(1)
Cash Flow Hedging [Member] | Other Income [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(10)	13	6
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(2)	14	(9)
Cash Flow Hedging [Member] | Interest rate contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	2	0
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(1)	(1)	(1)
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Compensation and Benefits [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	0	0	0
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Other General Expenses [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	0	0	0
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Interest Expense [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	2	0
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(1)	(1)	(1)
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Other Income [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	0	0	0
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(2)	(4)	(21)
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(14)	(10)	(34)
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Compensation and Benefits [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	11	(17)	(8)
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(5)	(12)	(9)
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Other General Expenses [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(3)	0	(19)
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	3	(9)	(16)
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(10)	(3)	0
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Other Income [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(10)	13	6
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion)	(2)	14	(9)
Net Investment Hedging [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income			4
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Compensation and Benefits [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income			0
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Other General Expenses [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income			0
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income			0
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Other Income [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income			$ 4