Income Taxes - Components Of Deferred Tax Balances (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Assets
Receivable allowances	$ 69	$ 72
Opioid-related litigation and claims	724	0
Compensation and benefit related accruals	305	331
Net operating loss and credit carryforwards	974	828
Lease obligations	539	482
Other	115	109
Subtotal	2,726	1,822
Less: valuation allowance	(864)	(833)
Total assets	1,862	989
Liabilities
Inventory valuation and other assets	(1,939)	(1,947)
Fixed assets and systems development costs	(196)	(202)
Intangibles	(411)	(531)
Lease right-of-use assets	(505)	(449)
Other	(37)	(56)
Total liabilities	(3,088)	(3,185)
Net deferred tax liability	(1,226)	(2,196)
Long-term deferred tax asset	185	59
Long-term deferred tax liability	$ (1,411)	$ (2,255)