Derivative financial instruments and risk management (Details 6) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Offsetting Liabilities
Derivative Asset, Collateral, Obligation to Return Cash, Offset	$ 0
Gross Amount of Recognized Liabilities	(167)	$ (56)
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount of Liabilities Presented in the Statement of Financial Position	(167)	(56)
Financial Instruments	28	19
Cash Collateral Pledged	0	0
Net Amount of Liabilities	139	37
Machinery, Energy & Transportation
Offsetting Liabilities
Gross Amount of Recognized Liabilities	(159)	(46)
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount of Liabilities Presented in the Statement of Financial Position	(159)	(46)
Financial Instruments	21	14
Cash Collateral Pledged	0	0
Net Amount of Liabilities	138	32
Financial Products
Offsetting Liabilities
Gross Amount of Recognized Liabilities	(8)	(10)
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount of Liabilities Presented in the Statement of Financial Position	(8)	(10)
Financial Instruments	7	5
Cash Collateral Pledged	0	0
Net Amount of Liabilities	$ 1	$ 5