FAIR VALUE MEASUREMENTS AND INVESTMENTS - Carrying Value and Estimated Fair Value of Outstanding Debt (Details) - USD ($) $ in Billions	Jul. 31, 2020	Jan. 31, 2020
Carrying Value | Senior Secured Credit Facilities | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	$ 8.6	$ 8.8
Carrying Value | First Lien Notes | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	21.3	20.5
Carrying Value | Unsecured Notes and Debentures | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	1.2	1.2
Carrying Value | Senior Notes | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	2.6	2.6
Carrying Value | EMC Notes | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	1.0	1.6
Carrying Value | VMware Notes and VMware Term Loan Facility | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	6.2	5.5
Carrying Value | Margin Loan Facility | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	4.0	4.0
Fair Value | Senior Secured Credit Facilities | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	8.6	9.0
Fair Value | First Lien Notes | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	25.1	23.9
Fair Value | Unsecured Notes and Debentures | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	1.5	1.5
Fair Value | Senior Notes | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	2.8	2.8
Fair Value | EMC Notes | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	1.1	1.6
Fair Value | VMware Notes and VMware Term Loan Facility | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	6.8	5.6
Fair Value | Margin Loan Facility | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding debt	$ 3.9	$ 3.9