Income Taxes - Components Of Deferred Tax Balances (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Assets
Receivable allowances	$ 58	$ 124
Compensation and benefit related accruals	345	593
Net operating loss and credit carryforwards	811	594
Long-term contractual obligations	59	107
Other	279	241
Subtotal	1,552	1,659
Less: valuation allowance	(751)	(503)
Total assets	801	1,156
Liabilities
Inventory valuation and other assets	(1,869)	(2,818)
Fixed assets and systems development costs	(158)	(224)
Intangibles	(644)	(921)
Change Healthcare Equity Investment	(814)	(773)
Other	(71)	(70)
Total liabilities	(3,556)	(4,806)
Net deferred tax liability	(2,755)	(3,650)
Long-term deferred tax asset	49	28
Long-term deferred tax liability	$ (2,804)	$ (3,678)