Derivatives and Hedging - Schedule of amounts of derivative gains (losses) recognized in the Consolidated Financial Statements (Details) - Cash Flow Hedging - Foreign exchange contracts - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	$ 1	$ (8)	$ 7	$ (18)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	(4)	(4)	6	(4)
Compensation and benefits
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	1	0	9	(2)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	0	13	1
Other General Expenses
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	1	(2)	2	(5)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	(1)	(1)	(2)	(1)
Interest Expense
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	0	0	0	0
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	(1)	(1)	(1)	(1)
Other Income (Expense)
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	(1)	(6)	(4)	(11)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	$ (2)	$ (2)	$ (4)	$ (3)