Off-Balance Sheet Risk and Guarantees, Concentrations of Credit Risk and Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Cash and cash equivalents:
Cash	$ 562	$ 616
Money market funds	1,024	842
Commercial paper	105	13
U.S. treasury securities	0	5
U.S. corporate obligations	25	4
Non-U.S. bank and other obligations	59	33
Short-term investments:
Commercial paper	223	11
U.S. Treasury securities	84	51
U.S. corporate obligations	202	51
U.S. non-governmental agency asset-backed securities	75	0
Non-qualified plan assets:
Money market funds	1	1
Domestic bond funds	3	3
Domestic equity funds	6	5
International equity funds	3	3
Blended equity funds	6	5
Common stock	1	2
Derivatives, net asset (liability):
Foreign currency contracts	(34)	(99)
Total financial instruments	2,345	1,546
Fair Value Based on Quoted Prices in Active Markets for Identical Assets (Level 1)
Cash and cash equivalents:
Cash	562	616
Money market funds	1,024	842
Commercial paper	0	0
U.S. treasury securities	0	5
U.S. corporate obligations	25	4
Non-U.S. bank and other obligations	59	33
Short-term investments:
Commercial paper	0	0
U.S. Treasury securities	84	51
U.S. corporate obligations	202	51
U.S. non-governmental agency asset-backed securities	0	0
Non-qualified plan assets:
Money market funds	1	1
Domestic bond funds	3	3
Domestic equity funds	6	5
International equity funds	3	3
Blended equity funds	6	5
Common stock	1	2
Derivatives, net asset (liability):
Foreign currency contracts	0	0
Total financial instruments	1,976	1,621
Fair Value Based on Significant Other Observable Inputs (Level 2)
Cash and cash equivalents:
Cash	0	0
Money market funds	0	0
Commercial paper	105	13
U.S. treasury securities	0	0
U.S. corporate obligations	0	0
Non-U.S. bank and other obligations	0	0
Short-term investments:
Commercial paper	223	11
U.S. Treasury securities	0	0
U.S. corporate obligations	0	0
U.S. non-governmental agency asset-backed securities	75	0
Non-qualified plan assets:
Money market funds	0	0
Domestic bond funds	0	0
Domestic equity funds	0	0
International equity funds	0	0
Blended equity funds	0	0
Common stock	0	0
Derivatives, net asset (liability):
Foreign currency contracts	(34)	(99)
Total financial instruments	$ 369	$ (75)