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Financial Instruments - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) interest_rate_swap	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Derivative [Line Items]
Pretax gains (losses) from euro-denominated notes included in cumulative translation adjustments	$ (520)	$ 193	$ 304
Number of interest rate swaps held | interest_rate_swap	26
Notional amount of derivative	$ 25,595	25,539
Pre tax net unrealized gain (loss) on derivatives maturing within next 12 months estimated to be reclassified from AOCI to sales	(184)
Available-for-sale debt securities included in Short-term investments	2,400
Available-for-sale debt securities maturing after one year through five years	11,100
Cash and cash equivalents	6,092	6,515	$ 8,524	$ 7,441
Fair value of loans payable and long-term debt, including current portion	25,600	25,700
Carrying value of Loans payable and long-term debt, including current portion	24,400	24,800
Total accounts receivable outstanding in excess of one year	$ 130
Percentage of accounts receivable represented by customers with largest balances (as percent)	40.00%
Cash collateral received from counterparties	$ 3	529
Significant Other Observable Inputs (Level 2)
Derivative [Line Items]
Cash and cash equivalents	6,100
Cash equivalents	5,200
Derivatives Designated as Hedging Instruments
Derivative [Line Items]
Notional amount of derivative	$ 14,386	14,398
Derivatives Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum planning cycle of third-party sales hedges (no more than)	2 years
Derivatives Not Designated as Hedging Instruments
Derivative [Line Items]
Notional amount of derivative	$ 11,209	$ 11,141
Derivatives Not Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum planning cycle of third-party sales hedges (no more than)	1 year

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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