Financial Instruments - Balance Sheet Grouping (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial assets		$ 24,175	$ 38,157
Selected financial liabilities	[1]	43,750	40,608
Cash and Cash Equivalents [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial assets		547	978
Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial assets		15,255	19,649
Other Current Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial assets	[2]	567	587
Long-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial assets		7,116	15,999
Other Noncurrent Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial assets	[3]	689	944
Short-Term Borrowings, including Current Portion of Long-term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial liabilities	[4]	10,688	10,159
Other Current Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial liabilities	[5]	443	645
Long-term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial liabilities	[4]	31,398	28,740
Other Noncurrent Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Selected financial liabilities	[6]	$ 1,222	$ 1,064

[1] We use a market approach in valuing financial instruments on a recurring basis. For additional information, see Note 1E. All of our financial assets and liabilities measured at fair value on a recurring basis use Level 2 inputs in the calculation of fair value, except less than 2% that use Level 1 inputs and money market funds measured at net asset value.

[2] As of December 31, 2016, derivative instruments at fair value include interest rate swaps ($26 million), foreign currency swaps ($43 million) and foreign currency forward-exchange contracts ($497 million) and, as of December 31, 2015, include interest rate swaps ($2 million), foreign currency swaps ($46 million) and foreign currency forward-exchange contracts ($538 million).

[3] As of December 31, 2016, derivative instruments at fair value include interest rate swaps ($599 million), foreign currency swaps ($36 million) and foreign currency forward-exchange contracts ($54 million) and, as of December 31, 2015, include interest rate swaps ($835 million), foreign currency swaps ($89 million) and foreign currency forward-exchange contracts ($20 million).

[4] We adopted a new standard as of January 1, 2016 that changed the presentation of debt issuance costs related to a recognized debt liability as a direct deduction from the carrying value of that associated debt, consistent with the presentation of a debt discount. See Note 1B for additional information.

[5] At December 31, 2016, derivative instruments at fair value include interest rate swaps ($1 million), foreign currency swaps ($300 million) and foreign currency forward-exchange contracts ($143 million) and, as of December 31, 2015, include interest rate swaps ($5 million), foreign currency swaps ($560 million) and foreign currency forward-exchange contracts ($80 million).

[6] At December 31, 2016, derivative instruments at fair value include interest rate swaps ($147 million) and foreign currency swaps ($1.1 billion) and, as of December 31, 2015, include interest rate swaps ($134 million), foreign currency swaps ($928 million) and foreign currency forward-exchange contracts ($1 million).