Operations and summary of significant accounting policies Operations and summary of significant accounting polices (Details 3- lease accounting) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid Expense and Other Assets, Current	$ 1,739	$ 1,748	$ 1,765
Property, Plant and Equipment, Net	12,904	13,548	13,574
Noncurrent deferred and refundable income taxes	1,411	1,362	1,439
Other Assets, Noncurrent	3,340	3,045	2,332
Accrued Liabilities, Current	3,750	3,546	3,573
Other Liabilities, Current	2,155	2,128	1,919
Long-term Debt, Due after One Year Machinery, Energy & Transportation, Noncurrent		7,643	8,005
Other Liabilities, Noncurrent	4,323	4,294	3,756
Retained Earnings (Accumulated Deficit)	$ 34,437	30,662	$ 30,427
Cumulative impact from adopting new lease guidance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid Expense and Other Assets, Current		(17)
Property, Plant and Equipment, Net		(26)
Noncurrent deferred and refundable income taxes		(77)
Other Assets, Noncurrent		713
Accrued Liabilities, Current		(27)
Other Liabilities, Current		209
Long-term Debt, Due after One Year Machinery, Energy & Transportation, Noncurrent		(362)
Other Liabilities, Noncurrent		538
Retained Earnings (Accumulated Deficit)		$ 235