CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Other Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury	Noncontrolling Interests	Opening retained earnings adjustment: adoption of new accounting standard	Opening retained earnings adjustment: adoption of new accounting standard Retained Earnings	Adjusted balance, April 1	Adjusted balance, April 1 Common Stock	Adjusted balance, April 1 Additional Paid-in Capital	Adjusted balance, April 1 Other Capital	Adjusted balance, April 1 Retained Earnings	Adjusted balance, April 1 Accumulated Other Comprehensive Income (Loss)	Adjusted balance, April 1 Treasury	Adjusted balance, April 1 Noncontrolling Interests
Beginning balance (shares) at Mar. 31, 2019		271,000										271,000
Beginning balance (shares) at Mar. 31, 2019							(81,000)										(81,000)
Beginning balance at Mar. 31, 2019	$ 8,287	$ 3	$ 6,435	$ (2)	$ 12,409	$ (1,849)	$ (8,902)	$ 193	$ 11	$ 11	$ 8,298	$ 3	$ 6,435	$ (2)	$ 12,420	$ (1,849)	$ (8,902)	$ 193
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employee plans (shares)		0
Issuance of shares under employee plans	5		22				$ (17)
Share-based compensation	26		26
Payments to noncontrolling interests	(39)							(39)
Other comprehensive income (loss)	71					71
Net income	466				423			43
Repurchase of common stock (shares)							(5,000)
Repurchase of common stock	(684)						$ (684)
Cash dividends declared	(73)				(73)
Other	(2)		0	1				(3)
Ending balance (shares) at Jun. 30, 2019		271,000
Ending balance (shares) at Jun. 30, 2019							(86,000)
Ending balance at Jun. 30, 2019	$ 8,068	$ 3	6,483	(1)	12,770	(1,778)	$ (9,603)	194
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 0.39
Beginning balance (shares) at Mar. 31, 2020		272,000										272,000
Beginning balance (shares) at Mar. 31, 2020	(110,000)						(110,000)										(110,000)
Beginning balance at Mar. 31, 2020	$ 5,309	$ 2	6,663	0	13,022	(1,703)	$ (12,892)	217	$ (13)	$ (13)	$ 5,296	$ 2	$ 6,663	$ 0	$ 13,009	$ (1,703)	$ (12,892)	$ 217
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employee plans (shares)		0
Issuance of shares under employee plans	(3)		21				$ (24)
Share-based compensation	23		23
Payments to noncontrolling interests	(43)							(43)
Other comprehensive income (loss)	(32)					(32)
Net income	483				444			39
Exercise of put right by noncontrolling shareholders of McKesson Europe	3		3
Cash dividends declared	(67)				(67)
Other	$ (7)		1		(2)			(6)
Ending balance (shares) at Jun. 30, 2020		272,000
Ending balance (shares) at Jun. 30, 2020	(110,000)						(110,000)
Ending balance at Jun. 30, 2020	$ 5,653	$ 2	$ 6,711	$ 0	$ 13,384	$ (1,735)	$ (12,916)	$ 207
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 0.41