Related Party Transactions - Net Parent Investment (Details) - IBM - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Related Party Transaction [Line Items]
Cash pooling and general financing activities/other	$ (1,515)	$ (2,853)
Allocation of Parent's corporate expenses/other	1,139	1,204
Related party sales and purchases	2,252	2,130
Related party intangible assets fee	60	60
Income taxes	716	245
Total Net transfers from Parent per Combined Statement of Equity	2,652	786
Income taxes	(716)	(245)
Allocation of Parent's stock-based compensation	(53)	(47)
Other	(89)	(100)
Total Net transfers from Parent per Combined Statement of Cash Flows	$ 1,794	$ 394