Segments of Business (Details)	3 Months Ended
	Jun. 30, 2019 USD ($) segment country	Jun. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Revenues
Total Revenues	$ 55,728,000,000	$ 52,607,000,000
Operating profit
Total operating profit	634,000,000	83,000,000
Corporate Expenses, Net	(175,000,000)	(123,000,000)
Interest Expense	(56,000,000)	(61,000,000)
Income from Continuing Operations Before Income Taxes	619,000,000	6,000,000
Pre-tax credits related to LIFO accounting	15,000,000	21,000,000
Proceeds from legal settlements		35,000,000
Pretax goodwill impairment charges	0	570,000,000
Net income (loss) from Change Healthcare	4,000,000	$ (56,000,000)
Gain (loss) from net investment hedges recorded in earnings	$ 10,000,000
U.S. Pharmaceutical and Specialty Solutions
Operating profit
Revenue derived from services, percentage (less than)	1.00%	1.00%
Pre-tax credits related to LIFO accounting	$ 15,000,000	$ 21,000,000
European Pharmaceutical Solutions
Segment Reporting Information [Line Items]
Number of countries in which entity segment operates | country	13
Operating profit
Revenue derived from services, percentage (less than)	10.00%
Pretax goodwill impairment charges		570,000,000
Medical-Surgical Solutions
Operating profit
Revenue derived from services, percentage (less than)	2.00%
Operating Segments
Revenues
Total Revenues	$ 55,728,000,000	52,607,000,000
Operating profit
Total operating profit	850,000,000	190,000,000
Operating Segments | U.S. Pharmaceutical and Specialty Solutions
Revenues
Total Revenues	44,165,000,000	40,977,000,000
Operating profit
Total operating profit	579,000,000	543,000,000
Operating Segments | European Pharmaceutical Solutions
Revenues
Total Revenues	6,710,000,000	6,935,000,000
Operating profit
Total operating profit	5,000,000	$ (560,000,000)
Revenue derived from services, percentage (less than)		10.00%
Operating Segments | Medical-Surgical Solutions
Revenues
Total Revenues	1,903,000,000	$ 1,703,000,000
Operating profit
Total operating profit	125,000,000	$ 93,000,000
Revenue derived from services, percentage (less than)		2.00%
Operating Segments | Other
Revenues
Total Revenues	2,950,000,000	$ 2,992,000,000
Operating profit
Total operating profit	141,000,000	114,000,000
Joint Venture | Change Healthcare JV
Operating profit
Net income (loss) from Change Healthcare	4,000,000	(56,000,000)
United States
Revenues
Total Revenues	46,321,000,000	42,890,000,000
Foreign
Revenues
Total Revenues	9,407,000,000	9,717,000,000
Canada | Other
Operating profit
Net restructuring charges recognized		38,000,000
Net restructuring charges recognized, after tax		38,000,000
Third Party Seller of Rexall Health | Rexall Health | Canada
Operating profit
Gain on escrow settlement, after tax		97,000,000
Gain on escrow settlement		97,000,000
Mckesson Europe Reporting Unit | Operating Segments | European Pharmaceutical Solutions
Operating profit
Pretax goodwill impairment charges		$ 570,000,000
Net Investment Hedge and Forward Contracts
Operating profit
Gain (loss) from net investment hedges recorded in earnings	25,000,000
United States | Pension Plan
Operating profit
Pre-tax settlement expense	$ 17,000,000