Quarterly Financial Information (Unaudited) - Schedule Of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 46,678	$ 47,899	$ 48,761	$ 47,546	$ 44,925	$ 46,484	$ 44,160	$ 43,476	$ 190,884	$ 179,045	$ 137,392
Gross profit	2,852	2,872	2,844	2,848	2,917	2,898	2,864	2,732	11,416	11,411	8,352
Income after income taxes:
Continuing operations	465	642	636	599	411	521	491	419	2,342	1,842	1,414
Discontinued operations	(21)	5	(6)	(10)	(267)	(10)	(14)	(8)	(32)	(299)	(156)
Net Income	444	647	630	589	144	511	477	411	2,310	1,543	1,258
Net income attributable to McKesson	$ 431	$ 634	$ 617	$ 576	$ 132	$ 472	$ 469	$ 403	$ 2,258	$ 1,476	$ 1,263
Diluted
Continuing operations (in dollars per share)	$ 1.97	$ 2.71	$ 2.65	$ 2.50	$ 1.69	$ 2.04	$ 2.05	$ 1.76	$ 9.84	$ 7.54	$ 6.08
Discontinued operations (in dollars per share)	(0.09)	0.02	(0.02)	(0.05)	(1.13)	(0.04)	(0.06)	(0.04)	(0.14)	(1.27)	(0.67)
Total (in dollars per share)	1.88	2.73	2.63	2.45	0.56	2.00	1.99	1.72	9.70	6.27	5.41
Basic
Continuing operations (in dollars per share)	1.99	2.74	2.68	2.53	1.72	2.07	2.08	1.79	9.96	7.66	6.19
Discontinued operations (in dollars per share)	(0.09)	0.02	(0.02)	(0.04)	(1.15)	(0.04)	(0.06)	(0.04)	(0.14)	(1.29)	(0.68)
Total (in dollars per share)	$ 1.90	$ 2.76	$ 2.66	$ 2.49	$ 0.57	$ 2.03	$ 2.02	$ 1.75	$ 9.82	$ 6.37	$ 5.51