Financial Assets & Liabilities - Kyndryl Common Stock (Details) $ in Millions				3 Months Ended	6 Months Ended
	May 23, 2022 USD ($) $ / shares	May 18, 2022 USD ($)	Nov. 03, 2021	Jun. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Financial assets and financial liabilities measured at fair value on a recurring basis:
Proceeds from short term credit		$ 357.0
Short-term debt				$ 5,981.0	$ 5,981.0	$ 6,787.0
Strike price | $ / shares	$ 13.95
Debt converted amount	$ 311.0
Repayment of debt	$ 46.0
Fair value of the swap				$ 88.0	$ 88.0
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]				Other accrued expenses and liabilities	Other accrued expenses and liabilities
Short term debt, fair value				$ 218.0	$ 218.0
Exchangeable debt
Financial assets and financial liabilities measured at fair value on a recurring basis:
Short-term debt				311.0	311.0
Other (income) and expense
Financial assets and financial liabilities measured at fair value on a recurring basis:
Unrealized loss					88.0
Changes in fair value of the debt				(93.0)
Kyndryl Holdings, Inc
Financial assets and financial liabilities measured at fair value on a recurring basis:
Ownership interest by stockholders (in percent)			19.90%
Amount of retained interest transferred	9.95%
Equity on conversion debt	22.3
Kyndryl Holdings, Inc | Other (income) and expense
Financial assets and financial liabilities measured at fair value on a recurring basis:
Unrealized loss				56.0	278.0
Kyndryl Holdings, Inc | Prepaid expenses and other current assets
Financial assets and financial liabilities measured at fair value on a recurring basis:
Investment Owned, at Fair Value				$ 436.0	$ 436.0	$ 807.0
Kyndryl Holdings, Inc
Financial assets and financial liabilities measured at fair value on a recurring basis:
Period in which shares are intended to be disposed of after separation			12 months