Reconciliation of Previously Reported Amounts to Revised and Restated Financial Statements - Consolidated Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018		Mar. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase in receivables	$ (947)	$ (464)	[1],[2]	$ (25)	[2]
Net cash provided by operating activities	1,783	2,567	[1],[2]	619	[2]
Cash collections related to deferred purchase price receivable	1,084	685	[1],[2]	359	[2]
Net cash used in investing activities	$ 69	719	[1],[2]	(565)	[2]
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase in receivables		74		193
Net cash provided by operating activities		3,105		837
Cash collections related to deferred purchase price receivable		147		141
Net cash used in investing activities		181		(783)
Accounting Standards Update 2016-15 | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase in receivables		(538)		(218)
Net cash provided by operating activities		(538)		(218)
Cash collections related to deferred purchase price receivable		538		218
Net cash used in investing activities		$ 538		$ 218

[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."