Goodwill Impairment Charges (Details) - USD ($)	3 Months Ended			6 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Goodwill [Line Items]
Goodwill and asset impairment charges	$ 0	$ 570,000,000	$ 350,000,000	$ 570,000,000	$ 350,000,000
Goodwill	10,627,000,000			10,627,000,000		$ 10,924,000,000
Goodwill impairment, tax benefit				0	$ 0
European Pharmaceutical Solutions
Goodwill [Line Items]
Goodwill and asset impairment charges		570,000,000		570,000,000
Goodwill	1,210,000,000			1,210,000,000		$ 1,850,000,000
Mckesson Europe Reporting Unit
Goodwill [Line Items]
Goodwill and asset impairment charges			350,000,000
Goodwill impairment, tax benefit			$ 0
Consumer Solutions Reporting Unit
Goodwill [Line Items]
Goodwill and asset impairment charges		$ 332,000,000
Discount rate (percent)		8.50%
Terminal growth rate (percent)		1.25%
Goodwill	466,000,000			466,000,000
Pharmacy Solutions Reporting Unit
Goodwill [Line Items]
Goodwill and asset impairment charges		$ 238,000,000
Discount rate (percent)		8.00%
Terminal growth rate (percent)		1.25%
Goodwill	$ 744,000,000			$ 744,000,000