Derivative instruments (Fair Value of Derivatives) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets
Total derivative assets, fair value	$ 244	$ 213
Liabilities
Total derivative liabilities, fair value	534	261
Derivatives designated as hedging instruments [Member]
Assets
Total derivative assets, fair value	244	213
Liabilities
Total derivative liabilities, fair value	534	260
Derivatives designated as hedging instruments [Member] | Foreign currency contracts [Member] | Other current assets/Other noncurrent assets [Member]
Assets
Total derivative assets, fair value	203	142
Derivatives designated as hedging instruments [Member] | Foreign currency contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	4	7
Derivatives designated as hedging instruments [Member] | Cross-currency swap contracts [Member] | Other current assets/Other noncurrent assets [Member]
Assets
Total derivative assets, fair value	0	0
Derivatives designated as hedging instruments [Member] | Cross-currency swap contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	523	250
Derivatives designated as hedging instruments [Member] | Interest rate swap contracts [Member] | Other current assets/Other noncurrent assets [Member]
Assets
Total derivative assets, fair value	41	71
Derivatives designated as hedging instruments [Member] | Interest rate swap contracts [Member] | Accrued liabilities/Other noncurrent liabilities [Member]
Liabilities
Total derivative liabilities, fair value	7	3
Derivatives not designated as hedging instruments [Member]
Assets
Total derivative assets, fair value	0	0
Liabilities
Total derivative liabilities, fair value	0	1
Derivatives not designated as hedging instruments [Member] | Foreign currency contracts [Member] | Other current assets [Member]
Assets
Total derivative assets, fair value	0	0
Derivatives not designated as hedging instruments [Member] | Foreign currency contracts [Member] | Accrued liabilities [Member]
Liabilities
Total derivative liabilities, fair value	$ 0	$ 1