Income Taxes - Reconciliation Between Effective Tax Rate On Income From Continuing Operations And Statutory Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income tax expense (benefit) at federal statutory rate	$ (1,057)	$ 240	$ 128
State income taxes, net of federal tax benefit	(206)	(41)	70
Tax effect of foreign operations	(77)	(81)	(86)
Unrecognized tax benefits and settlements	41	(7)	20
Non-deductible goodwill	14	7	357
Opioid-related litigation and claims	715	0	0
Net tax benefit on intellectual property transfer	(105)	0	(42)
Tax-free gain on investment exit	0	(87)	0
Impact of change in U.S. tax rate on temporary differences	0	0	(81)
Capital loss carryback	0	(19)	0
Other, net	(20)	6	(10)
Income tax expense (benefit)	$ (695)	$ 18	$ 356