Relationship with IBM and Related Party Transactions - Borrowing, Services, and Other Arrangements (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Related party transactions
Related party borrowings outstanding	$ 14,727		$ 16,945
Interest expense incurred on related party borrowings	49	$ 74
Accounts payable to related party	813		336
IBM
Related party transactions
Selling, general and administrative expense with related party	34	48
Accounts payable to related party	813		$ 336
IBM \| Financing cost \| Debt payable to IBM
Related party transactions
Interest expense incurred on related party borrowings	49	74
IBM \| Sales of returned equipment \| Other (income) and expense
Related party transactions
Net profit on transaction with related party	$ 3	$ 2

Amount of net profit from transactions with related parties.

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Amount for accounts payable to related parties.

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Amount of selling, general and administrative expenses resulting from transactions, excluding transactions that are eliminated in consolidated or combined financial statements, with related party.

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