Segments of Business - Schedule Of Segment Information (Details) - USD ($) $ 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
Revenues
Total Revenues	$ 46,678	$ 47,899	$ 48,761	$ 47,546	$ 44,925	$ 46,484	$ 44,160	$ 43,476	$ 190,884	$ 179,045	$ 137,392
Operating profit
Total									3,545	2,968	2,439
Interest Expense									(353)	(374)	(300)
Income From Continuing Operations Before Income Taxes									3,250	2,657	2,171
Depreciation and amortization
Total									885	1,017	735
Expenditures for long-lived assets
Total									488	376	278
United States
Revenues
Total Revenues									158,255	142,810	122,426
Foreign
Revenues
Total Revenues									32,629	36,235	14,966
Operating Segments
Revenues
Total Revenues									190,884	179,045	137,392
Operating profit
Total									4,072	3,485	2,920
Operating Segments | Distribution Solutions
Revenues
Total Revenues									187,999	175,976	134,062
Operating profit
Total									3,553	3,047	2,472
Depreciation and amortization
Total									669	750	446
Expenditures for long-lived assets
Total									306	301	179
Operating Segments | Distribution Solutions | Reportable Subsegments | North America pharmaceutical distribution and services
Revenues
Total Revenues									158,469	143,711	123,929
Operating Segments | Distribution Solutions | Reportable Subsegments | International pharmaceutical distribution and services
Revenues
Total Revenues									23,497	26,358	4,485
Operating Segments | Distribution Solutions | Reportable Subsegments | Medical-Surgical distribution and services
Revenues
Total Revenues									6,033	5,907	5,648
Operating Segments | Technology Solutions
Revenues
Total Revenues									2,885	3,069	3,330
Operating profit
Total									519	438	448
Depreciation and amortization
Total									107	156	169
Expenditures for long-lived assets
Total									15	27	47
Corporate Expenses, Net
Operating profit
Corporate Expenses, Net									(469)	(454)	(449)
Depreciation and amortization
Total									109	111	120
Expenditures for long-lived assets
Total									167	48	52
Segment Reconciling Items
Operating profit
Interest Expense									$ (353)	$ (374)	$ (300)