Quarterly Financial Information (Unaudited) (Schedule Of Quarterly Financial Information) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2013
Quarterly Financial Information [Line Items]
Revenues	$ 44,925		$ 46,484		$ 44,160		$ 43,476		$ 37,832		$ 34,336		$ 32,985		$ 32,239		$ 179,045	[1]	$ 137,392	[1]	$ 122,196	[1]
Gross profit	2,917	[2]	2,898	[2]	2,864	[2]	2,732	[2]	2,551	[3]	1,850	[3]	2,021	[3]	1,930		11,411		8,352		6,881
Income from continuing operations	411	[2],[4]	521	[2]	491	[2]	419	[2]	399	[3],[5]	164	[3],[5]	423	[3]	428	[3]	1,842		1,414		1,363
Income (Loss) from Discontinued Operations, Net of Tax	(267)	[6]	(10)		(14)		(8)		(34)		(99)	[7]	(19)		(4)		(299)		(156)		(25)
Net Income	144		511		477		411		365		65		404		424		1,543		1,258		1,338
Net loss attributable to noncontrolling interests	(12)	[8]	(39)	[8]	(8)	[8]	(8)	[8]	5	[9]	0	[9]	0	[9]	0	[9]	(67)		5		0
Net Income Attributable to McKesson	$ 132		$ 472		$ 469		$ 403		$ 370		$ 65		$ 404		$ 424		$ 1,476		$ 1,263		$ 1,338
Earnings (Loss) Per Common Share Attributable to McKesson
Diluted	$ 0.56	[10]	$ 2.00	[10]	$ 1.99	[10]	$ 1.72	[10]	$ 1.58	[10]	$ 0.28	[10]	$ 1.74	[10]	$ 1.83	[10]	$ 6.27	[10]	$ 5.41	[10]	$ 5.59	[10]
Continuing operations	$ 1.69	[10]	$ 2.04	[10]	$ 2.05	[10]	$ 1.76	[10]	$ 1.72	[10]	$ 0.70	[10]	$ 1.82	[10]	$ 1.84	[10]	$ 7.54	[10]	$ 6.08	[10]	$ 5.69	[10]
Discontinued operations	$ (1.13)	[10]	$ (0.04)	[10]	$ (0.06)	[10]	$ (0.04)	[10]	$ (0.14)	[10]	$ (0.42)	[10]	$ (0.08)	[10]	$ (0.01)	[10]	$ (1.27)	[10]	$ (0.67)	[10]	$ (0.10)	[10]
Basic	$ 0.57	[10]	$ 2.03	[10]	$ 2.02	[10]	$ 1.75	[10]	$ 1.61	[10]	$ 0.28	[10]	$ 1.76	[10]	$ 1.86	[10]	$ 6.37	[10]	$ 5.51	[10]	$ 5.71	[10]
Continuing operations	$ 1.72	[10]	$ 2.07	[10]	$ 2.08	[10]	$ 1.79	[10]	$ 1.76	[10]	$ 0.71	[10]	$ 1.85	[10]	$ 1.88	[10]	$ 7.66	[10]	$ 6.19	[10]	$ 5.81	[10]
Discontinued operations	$ (1.15)	[10]	$ (0.04)	[10]	$ (0.06)	[10]	$ (0.04)	[10]	$ (0.15)	[10]	$ (0.43)	[10]	$ (0.09)	[10]	$ (0.02)	[10]	$ (1.29)	[10]	$ (0.68)	[10]	$ (0.10)	[10]

[1] Net revenues were attributed to geographic areas based on the customers’ shipment locations.

[2] Financial results for the first, second, third and fourth quarters of 2015 include pre-tax charges in our Distribution Solutions segment related to our last-in-first-out (“LIFO”) method of accounting for inventories of $98 million, $94 million, $95 million and $50 million, which were recorded in cost of sales.

[3] Financial results for the second, third and fourth quarters of 2014 include pre-tax charges in our Distribution Solutions segment related to our LIFO method of accounting for inventories of $44 million, $142 million and $125 million, which were recorded in cost of sales. The fourth quarter of 2014 also includes a $40 million pre-tax charge to cost of sales within our Distribution Solutions segment representing the reversal of a step-up to fair value of Celesio’s inventory at the date of acquisition. Our after-tax portion of this charge from continuing operations (after allocation to noncontrolling interests) was $21 million.

[4] Fourth quarter of 2015 includes a non-cash after-tax charge of $150 million related to the settlement of controlled substance distribution claims.

[5] Financial results for the third quarter of 2014 include an income tax charge of $122 million relating to our litigation with the Canadian Revenue Agency.

[6] Fourth quarter of 2015 includes $235 million non-cash after-tax impairment charges related to our Brazilian pharmaceutical distribution business.

[7] Financial results for the third quarter of 2014 include an $80 million after-tax impairment charge related to our International Technology Business, which was sold in part during the second quarter of 2015.

[8] Primarily reflects the guaranteed dividends of $50 million for the first nine months of 2015 and the recurring compensation of $12 million for the fourth quarter of 2015. McKesson is obligated to pay these amounts to the noncontrolling shareholders of Celesio under the Domination Agreement which became effective in December 2014.

[9] Primarily represents the noncontrolling shareholders’ portion of net loss from Celesio.

[10] Certain computations may reflect rounding adjustments.