Operations and summary of significant accounting policies (Details 2- Basis of presentation) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Ownership percentage of investments in companies below which the entity must exercise significant influence in order to be accounted for under the equity method	20.00%
Amount reclassified from other current liabilities to customer advances			$ 233
Payments made for terminated contract with a related guarantee	$ 0
Variable Interest Entity
Receivables - trade and other	8,802	$ 7,370	7,436
Receivables - finance	8,650		8,757
Long-term receivables - finance	13,286		13,542
Guarantees	1,978		2,105
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity
Receivables - trade and other	31		34
Receivables - finance	45		42
Long-term receivables - finance	26		38
Investments in unconsolidated affiliated companies	29		39
Guarantees	0		259
Total	$ 131		$ 412
Minimum
Variable Interest Entity
Equity Method Investment, Ownership Percentage	20.00%

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of investment in equity method investee and investment in and advance to affiliate.

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An amount representing an agreement for an unconditional promise by the maker to pay the Company (holder) a definite sum of money within one year from the balance sheet date (or the normal operating cycle, whichever is longer), net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the debt. The debt also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. This amount does not include amounts related to receivables held-for-sale.

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The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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