Acquisitions - Fiscal 2017 Acquisitions (Details) - USD ($)		12 Months Ended
	May 05, 2016	Mar. 31, 2019	Mar. 31, 2018		Mar. 31, 2017
Business Acquisition [Line Items]
Payments for acquisitions, net of cash acquired		$ 365,000,000	$ 203,000,000	[1],[2]	$ 434,000,000	[2]
Goodwill		7,606,000,000	7,619,000,000		1,855,000,000
Xchanging
Business Acquisition [Line Items]
Total consideration transferred	$ 693,000,000
Payments for acquisitions, net of cash acquired	492,000,000
Acquisition related costs	17,000,000
Current assets acquired	396,000,000
Noncurrent assets	99,000,000
Intangible assets(2)	582,000,000
Current liabilities	267,000,000
Long-term liabilities	516,000,000
Goodwill	680,000,000
Expected tax deductible amount of goodwill acquired	0
Non-controlling interest	$ 281,000,000
Customer relationships | Xchanging
Business Acquisition [Line Items]
Useful lives (years)	15 years
GBS
Business Acquisition [Line Items]
Goodwill		4,599,000,000	4,531,000,000		1,470,000,000
GBS | Xchanging
Business Acquisition [Line Items]
Goodwill	$ 646,000,000
GIS
Business Acquisition [Line Items]
Goodwill		$ 3,007,000,000	$ 3,088,000,000		$ 385,000,000
GIS | Xchanging
Business Acquisition [Line Items]
Goodwill	$ 34,000,000
Minimum | Developed technology | Xchanging
Business Acquisition [Line Items]
Useful lives (years)	7 years
Minimum | Trade names | Xchanging
Business Acquisition [Line Items]
Useful lives (years)	3 years
Maximum | Developed technology | Xchanging
Business Acquisition [Line Items]
Useful lives (years)	8 years
Maximum | Trade names | Xchanging
Business Acquisition [Line Items]
Useful lives (years)	5 years

[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.

[2] Fiscal 2018 and fiscal 2017 have been adjusted to give effect to the retrospective adoption of ASU 2016-15. See Note 22 - "Reconciliation of Previously Reported Amounts to Recast Financial Statements."