Derivatives and Hedging - Schedule of amounts of derivative gains (losses) recognized in the Consolidated Financial Statements (Details) - Cash Flow Hedging [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	$ (14)	$ (3)	$ (1)	$ 4
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	4	(7)	(16)
Interest rate contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0	0
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	0	0	(1)
Foreign exchange contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(14)	(3)	(1)	4
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	4	(7)	(15)
Compensation and Benefits [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(8)	(2)	(2)	14
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	2	(1)	3	(4)
Compensation and Benefits [Member] | Interest rate contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0	0
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	0	0	0
Compensation and Benefits [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(8)	(2)	(2)	14
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	2	(1)	3	(4)
Other General Expenses [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(2)	(3)	(1)	(1)
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	3	(1)	3
Other General Expenses [Member] | Interest rate contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0	0
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	0	0	0
Other General Expenses [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(2)	(3)	(1)	(1)
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	3	(1)	3
Interest Expense [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0	0
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	(2)	(3)	(6)	(9)
Interest Expense [Member] | Interest rate contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0	0
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	0	0	(1)
Interest Expense [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0	0
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	(2)	(3)	(6)	(8)
Other Income (Expense) [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(4)	2	2	(9)
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	5	(3)	(6)
Other Income (Expense) [Member] | Interest rate contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	0	0	0	0
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	0	0	0
Other Income (Expense) [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Gain (loss) recognized in accumulated other comprehensive income	(4)	2	2	(9)
Gain (Loss) reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	$ 0	$ 5	$ (3)	$ (6)