Divestitures - Cash Flow (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018		Mar. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation expense	$ 820	$ 709		$ 338
Capital expenditures	(297)	(224)	[1],[2]	$ (246)	[2]
USPS Separation | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation expense	16	70
Amortization	17	99
Capital expenditures	0	(18)
Gain on dispositions	$ 24	$ 0

[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."