Derivative instruments (Fair Value of Derivatives) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Assets
Total derivative assets, fair value	$ 281	$ 244
Liabilities
Total derivative liabilities, fair value	492	534
Derivatives designated as hedging instrument [Member]
Assets
Total derivative assets, fair value	281	244
Liabilities
Total derivative liabilities, fair value	492	534
Derivatives designated as hedging instrument [Member] | Foreign currency contracts [Member] | Other current assets/Other noncurrent assets [Member]
Assets
Total derivative assets, fair value	7	203
Derivatives designated as hedging instrument [Member] | Foreign currency contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	179	4
Derivatives designated as hedging instrument [Member] | Cross currency swap contracts [Member] | Other noncurrent assets [Member]
Assets
Total derivative assets, fair value	224	0
Derivatives designated as hedging instrument [Member] | Cross currency swap contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	308	523
Derivatives designated as hedging instrument [Member] | Interest rate swap contracts [Member] | Other noncurrent assets [Member]
Assets
Total derivative assets, fair value	40	41
Derivatives designated as hedging instrument [Member] | Interest rate swap contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	5	7
Derivatives designated as hedging instrument [Member] | Forward interest rate contract [Member] | Other current assets [Member]
Assets
Total derivative assets, fair value	10
Derivatives designated as hedging instrument [Member] | Forward interest rate contract [Member] | Accrued liabilities [Member]
Liabilities
Total derivative liabilities, fair value	0
Derivatives not designated as hedging instrument [Member]
Assets
Total derivative assets, fair value	0	0
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	0
Derivatives not designated as hedging instrument [Member] | Foreign currency contracts [Member] | Accrued liabilities [Member]
Liabilities
Total derivative liabilities, fair value	$ 0	$ 0