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
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	$ 6	$ (10)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	10	0
Compensation and benefits
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	8	(2)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	13	1
Other General Expenses
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	1	(3)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	(1)	0
Interest Expense
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	0	0
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	0	0
Other Income (Expense)
Derivative [Line Items]
Gain (Loss) Recognized in Accumulated Other Comprehensive Loss:	(3)	(5)
Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion):	$ (2)	$ (1)