Goodwill (Details) - USD ($)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill	$ 7,606,000,000	$ 7,619,000,000
Acquisitions	1,358,000,000	228,000,000
Impairment Losses	(6,794,000,000)	0	$ 0	[1]
Divestitures		(12,000,000)
Foreign currency translation	(153,000,000)	(229,000,000)
Goodwill, gross	11,573,000,000	10,368,000,000
Accumulated impairment losses	(9,556,000,000)	(2,762,000,000)
Goodwill	2,017,000,000	7,606,000,000	7,619,000,000
GBS
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill	4,599,000,000	4,531,000,000
Acquisitions	1,288,000,000	228,000,000
Impairment Losses	(3,789,000,000)
Divestitures		(12,000,000)
Foreign currency translation	(81,000,000)	(148,000,000)
Goodwill, gross	6,507,000,000	5,300,000,000
Accumulated impairment losses	(4,490,000,000)	(701,000,000)
Goodwill	2,017,000,000	4,599,000,000	4,531,000,000
GIS
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill	3,007,000,000	3,088,000,000
Acquisitions	70,000,000	0
Impairment Losses	(3,005,000,000)
Divestitures		0
Foreign currency translation	(72,000,000)	(81,000,000)
Goodwill, gross	5,066,000,000	5,068,000,000
Accumulated impairment losses	(5,066,000,000)	(2,061,000,000)
Goodwill	$ 0	$ 3,007,000,000	$ 3,088,000,000

[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.