Summary of Significant Accounting Policies (Details)		3 Months Ended	12 Months Ended
	May 31, 2019	Sep. 30, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	[1]	Apr. 01, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amortization period			5 years
Goodwill impairment losses			$ 6,794,000,000	$ 0	$ 0
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease assets							$ 1,700,000,000
Lease liabilities							$ 1,800,000,000
Accounting Standards Update 2017-04
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill impairment losses		$ 6,794,000,000
GBS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill impairment losses			3,789,000,000
GBS | Accounting Standards Update 2017-04
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill impairment losses		3,789,000,000
GIS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill impairment losses			$ 3,005,000,000
GIS | Accounting Standards Update 2017-04
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill impairment losses		$ 3,005,000,000
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | USPS Separation
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Share exchange ratio	0.5

[1] As a result of the USPS Separation, the Consolidated Statements of Operations, Consolidated Balance Sheets, and related financial information reflect USPS's operations and assets and liabilities as discontinued operations for all periods presented. The cash flows of USPS have not been segregated and are included in the Consolidated Statement of Cash flows for the fiscal year ended March 31, 2018 and through the separation date of May 31, 2018 in the Consolidated Statement of Cash Flows for the fiscal year ended March 31, 2019.