Income Taxes - Narrative (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Mar. 09, 2020	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Tax Contingency [Line Items]
Income tax expense (benefit) rates (percent)			(13.80%)	1.60%	58.40%
Statutory federal income tax rate (percent)				21.00%	21.00%
Research and development credit			$ 5	$ 7	$ 7
Impact of opioid-related claims			8,100
After-tax impact of opioid-related claims			6,800
Deferred tax benefit			908	342	(189)
Unrecognized tax benefits				(91)
Net discrete tax benefit			105		42
Net gain from sale of equity method investment, pre-tax			0	0	56
Non-cash pre-tax charge			69	2	1,797
Valuation allowance		$ 833	864	833
Increase (decrease) in valuation allowance			31
Unrecognized tax benefits		958	1,754	958	1,052	$ 1,183
Unrecognized tax benefits that would Impact income tax expense and the effective tax rate			1,300
Decrease in unrecognized tax benefits				91
Amount of decrease in unrecognized tax benefits that is reasonably possible in the next twelve months			93
Income tax expense (benefit), before any tax effect, related to accrued interest and penalties			9	23	33
Accrued interest and penalties on unrecognized tax benefits		91	101	91
Undistributed earnings of foreign operations			6,000
Change Healthcare
Income Tax Contingency [Line Items]
Net gain from sale of equity method investment, pre-tax	$ 414
Change Healthcare | Corporate Joint Venture
Income Tax Contingency [Line Items]
Net gain from sale of equity method investment, pre-tax		$ 414
Federal
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards			2,400
State
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards			3,900
Foreign Tax Authority
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards			2,200
International
Income Tax Contingency [Line Items]
Charge for remeasurement to fair value				275
Non-cash pre-tax charge			69	$ 2	$ 1,776
Pending and Future Opioid-Related Claims
Income Tax Contingency [Line Items]
Deferred tax benefit			1,300
Unrecognized tax benefits			455
Decrease in unrecognized tax benefits			(455)
Capital Loss Carryforward | Foreign Tax Authority
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards			$ 783