Derivative instruments (Fair Value of Derivatives) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets
Total derivative assets, fair value	$ 475	$ 408
Liabilities
Total derivative liabilities, fair value	491	576
Derivatives designated as hedging instrument [Member]
Assets
Total derivative assets, fair value	475	407
Liabilities
Total derivative liabilities, fair value	491	576
Derivatives designated as hedging instrument [Member] | Foreign currency contracts [Member] | Other current assets/Other assets [Member]
Assets
Total derivative assets, fair value	238	181
Derivatives designated as hedging instrument [Member] | Foreign currency contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	8	26
Derivatives designated as hedging instrument [Member] | Cross-currency swap contracts [Member] | Other current assets/Other assets [Member]
Assets
Total derivative assets, fair value	143	170
Derivatives designated as hedging instrument [Member] | Cross-currency swap contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	429	401
Derivatives designated as hedging instrument [Member] | Interest rate swap contracts [Member] | Other current assets/Other assets [Member]
Assets
Total derivative assets, fair value	94	56
Derivatives designated as hedging instrument [Member] | Interest rate swap contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	54	149
Derivatives not designated as hedging instrument [Member]
Assets
Total derivative assets, fair value	0	1
Liabilities
Total derivative liabilities, fair value	0	0
Derivatives not designated as hedging instrument [Member] | Foreign currency contracts [Member] | Other current assets [Member]
Assets
Total derivative assets, fair value	0	1
Derivatives not designated as hedging instrument [Member] | Foreign currency contracts [Member] | Accrued liabilities [Member]
Liabilities
Total derivative liabilities, fair value	$ 0	$ 0