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Segments of Business (Details) £ in Millions, $ in Millions, $ in Millions				3 Months Ended					9 Months Ended
	Dec. 11, 2019 USD ($)	May 23, 2018 USD ($)	May 23, 2018 CAD ($)	Dec. 31, 2019 USD ($) country	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) segment country	Dec. 31, 2018 USD ($)	Dec. 31, 2019 GBP (£) country	Sep. 30, 2019 GBP (£)	Mar. 31, 2019 USD ($)	Mar. 31, 2019 GBP (£)	Dec. 31, 2018 GBP (£)
Segment Reporting Information [Line Items]
Long-term debt outstanding				$ 7,700					$ 7,700				$ 7,600
Number of reportable segments | segment									3
Revenues
Total Revenues				59,172			$ 56,208		$ 172,516	$ 161,890
Operating profit
Total operating profit				360			683		1,620	1,455
Corporate Expenses, Net				(211)			(190)		(750)	(480)
Interest Expense				(64)			(67)		(184)	(194)
Income (Loss) from Continuing Operations Before Income Taxes				294			650		(57)	1,243
Pre-tax credits related to LIFO accounting									114	64
Proceeds from legal settlements							104			139
Pre-tax charge related to customer bankruptcy							60			60
Goodwill and other asset impairment charges				30			35		113	671
Asset impairment Charge, net of tax				30			35
Pretax goodwill impairment charges				2			21		2	591
After-tax goodwill impairment										591
Net income (loss) from Change Healthcare				28			50		1,478	162
Net restructuring, impairment and related charges recognized				136			110		204	288
Net restructuring, impairment and related charges recognized, after tax				115			92		167	244
U.S. Pharmaceutical and Specialty Solutions
Operating profit
Pre-tax credits related to LIFO accounting				66			21		114	64
After-tax credit related to LIFO accounting				$ 49			16		84	47
Pretax goodwill impairment charges									$ 0
European Pharmaceutical Solutions
Segment Reporting Information [Line Items]
Number of countries in which entity segment operates | country				13					13		13
Operating profit
Goodwill and other asset impairment charges				$ 64					$ 64
Asset impairment Charge, net of tax				53					53
Pretax goodwill impairment charges									0	570
After-tax goodwill impairment								$ 570		570
Medical-Surgical Solutions
Operating profit
Pretax goodwill impairment charges									0
Other
Operating profit
Pretax goodwill impairment charges									2
Operating Segments
Revenues
Total Revenues				59,172			56,208		172,516	161,890
Operating profit
Total operating profit				569			907		877	1,917
Operating Segments | U.S. Pharmaceutical and Specialty Solutions
Revenues
Total Revenues				46,923			44,279		137,067	126,866
Operating profit
Total operating profit				$ 687			$ 671		$ 1,905	$ 1,824
Revenue derived from services, percentage (less than)				1.00%			1.00%		1.00%	1.00%
Operating Segments | European Pharmaceutical Solutions
Revenues
Total Revenues				$ 6,931			$ 6,911		$ 20,239	$ 20,485
Operating profit
Total operating profit				$ (303)			$ 26		$ (297)	$ (524)
Revenue derived from services, percentage (less than)				10.00%			10.00%		10.00%	10.00%
Operating Segments | Medical-Surgical Solutions
Revenues
Total Revenues				$ 2,141			$ 2,012		$ 6,100	$ 5,663
Operating profit
Total operating profit				$ 124			$ 136		$ 378	$ 334
Revenue derived from services, percentage (less than)				2.00%			2.00%		2.00%	2.00%
Operating Segments | Other
Revenues
Total Revenues				$ 3,177			$ 3,006		$ 9,110	$ 8,876
Operating profit
Total operating profit				61			74		(1,109)	283
Joint Venture
Operating profit
Pre-tax dilution loss from reduction of ownership									(246)
Pre-tax credit recognized on relief from potential future obligations										90
After-tax credit recognized on relief from potential future obligations										66
Joint Venture | Change Healthcare JV
Operating profit
Pre-tax impairment charge									1,200
After-tax impairment charge									864
Net income (loss) from Change Healthcare				28			50		75	162
United States
Revenues
Total Revenues				49,310			46,523		143,924	133,186
Foreign
Revenues
Total Revenues				9,862			9,685		28,592	28,704
Canada | Other
Operating profit
Net restructuring charges recognized										89
Net restructuring charges recognized, after tax										83
Rexall Health
Operating profit
Goodwill and other asset impairment charges							56		32	56
Asset impairment Charge, net of tax							56		32	56
Third Party Seller of Rexall Health | Rexall Health | Canada
Operating profit
Escrow settlement gain, pre-tax		$ 97	$ 125							97
Escrow settlement gain, net of tax										97
United States | Pension Plan
Operating profit
Pre-tax settlement expense					$ 105	$ 17			122
After-tax settlement expense					$ 78	$ 12			90
Related to Two Counties
Operating profit
Pre-tax litigation and other-related expenses									82
After-tax litigation and other-related expenses									61
In re: National Prescription Opioid Litigation
Operating profit
Pre-tax litigation and other-related expenses				36					190
Enterprise Information Solutions
Operating profit
Pre-tax gain on sale of equity method investment							56
After-tax gain on sale of equity method investment							41
Strategic Growth Initiative Plan - Relocation of Corporate Headquarters
Operating profit
Net restructuring, impairment and related charges recognized							31			31
Net restructuring, impairment and related charges recognized, after tax							$ 23			$ 23
Held-for-sale | German Wholesale Joint Venture
Operating profit
Impairment loss	$ 282			282					282
Impairment loss, after tax	$ 282			$ 282					$ 282
British Pound Sterling Denominated Notes | Term Loan
Segment Reporting Information [Line Items]
Long-term debt outstanding | £											£ 450	£ 450		£ 450	£ 450

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