Acquisitions and other investments - Narrative (Details) - USD ($) $ in Millions							1 Months Ended	3 Months Ended					9 Months Ended
	Mar. 03, 2023	Jan. 03, 2023	Dec. 28, 2022	Aug. 31, 2022	Nov. 24, 2021	Oct. 29, 2021	Mar. 31, 2023	May 31, 2023	Nov. 30, 2022	May 31, 2022	Feb. 28, 2022	Nov. 30, 2021	May 31, 2023	May 31, 2022	Nov. 23, 2021	Oct. 28, 2021
Business Acquisition [Line Items]
Goodwill, purchase adjustments													$ 252
Gain on sale of equity method investments													1,691	$ 421
Goodwill				$ 22,280				$ 28,371					28,371
VillageMD
Business Acquisition [Line Items]
Fair value of equity consideration		$ 1,750
Noncontrolling interest, ownership percentage by parent		53.00%
Debt instrument, fee amount, credit		$ 220
VillageMD | Line of Credit
Business Acquisition [Line Items]
Face amount		2,250
VillageMD | Line of Credit | Term Loan
Business Acquisition [Line Items]
Face amount		1,750
VillageMD | Line of Credit | Credit facilities
Business Acquisition [Line Items]
Face amount		500
VillageMD | Cigna
Business Acquisition [Line Items]
Fair value of equity consideration		2,500
VillageMD
Business Acquisition [Line Items]
Purchase price					$ 5,200
Fair value of equity consideration					683
Goodwill, purchase adjustments									$ 125
Intangible assets					$ 1,621
Outstanding equity interest percentage					63.00%										30.00%
Cash consideration, gross					$ 4,000
Promissory note					1,200
Business combination, consideration transferred to existing stockholders					2,900
Value of purchase tender offer					1,900
Cash consideration for preferred units					1,100
Gain related to fair value of company's previously held minority equity interest												$ 1,597
Pre-tax gain related to conversion of previously held investment in convertible debt securities												577
Gain on sale of equity method investments											$ 2,200
Goodwill					8,166
VillageMD | Provider networks
Business Acquisition [Line Items]
Intangible assets					$ 1,200
Useful life of intangible assets					15 years
VillageMD | Trade Names
Business Acquisition [Line Items]
Intangible assets					$ 295
Useful life of intangible assets					13 years
VillageMD | Technology-Based Intangible Assets
Business Acquisition [Line Items]
Intangible assets					$ 76
Useful life of intangible assets					5 years
Shields Health Solutions Parent, LLC
Business Acquisition [Line Items]
Cash consideration, subject to purchase price adjustments						$ 969
Fair value of equity consideration						13
Goodwill, purchase adjustments									$ 72
Intangible assets						$ 1,060
Outstanding equity interest percentage			30.00%			70.00%										25.00%
Cash consideration, gross			$ 1,400
Gain on sale of equity method investments												$ 402
Goodwill						$ 1,529
Shields Health Solutions Parent, LLC | Trade Names
Business Acquisition [Line Items]
Intangible assets						$ 47
Useful life of intangible assets						13 years
Shields Health Solutions Parent, LLC | Technology-Based Intangible Assets
Business Acquisition [Line Items]
Intangible assets						$ 117
Useful life of intangible assets						5 years
Shields Health Solutions Parent, LLC | Customer Relationships
Business Acquisition [Line Items]
Intangible assets						$ 896
Useful life of intangible assets						13 years
CareCentrix, Inc
Business Acquisition [Line Items]
Cash consideration, subject to purchase price adjustments				327
Purchase price							$ 378
Fair value of equity consideration				66
Business combination, consideration transferred, employees				12
Intangible assets				$ 426
Outstanding equity interest percentage				55.00%			45.00%
Cash consideration, gross				$ 339
Goodwill				509
CareCentrix, Inc | Trade Names
Business Acquisition [Line Items]
Intangible assets				$ 93
Useful life of intangible assets				13 years
CareCentrix, Inc | Technology-Based Intangible Assets
Business Acquisition [Line Items]
Intangible assets				$ 86
Useful life of intangible assets				5 years
CareCentrix, Inc | Customer Relationships
Business Acquisition [Line Items]
Intangible assets				$ 247
Useful life of intangible assets				13 years
Other Acquisitions
Business Acquisition [Line Items]
Cash consideration, net								37		$ 36			$ 127	$ 153
Summit Health-CityMD
Business Acquisition [Line Items]
Cash consideration, subject to purchase price adjustments		7,000
Purchase price		4,850
Fair value of equity consideration		1,971
Deferred consideration		100
Business combination, consideration transferred, employees		87
Summit debt paid at closing		1,900
Goodwill, purchase adjustments								$ (71)
Intangible assets		3,359
Goodwill		5,622
Summit Health-CityMD | Preferred Partnership Interest
Business Acquisition [Line Items]
Fair value of equity consideration		2,050
Summit Health-CityMD | Provider networks
Business Acquisition [Line Items]
Intangible assets		$ 1,900
Useful life of intangible assets		15 years
Summit Health-CityMD | Trade Names
Business Acquisition [Line Items]
Intangible assets		$ 1,500
Summit Health-CityMD | Minimum | Trade Names
Business Acquisition [Line Items]
Useful life of intangible assets		11 years
Summit Health-CityMD | Maximum | Trade Names
Business Acquisition [Line Items]
Useful life of intangible assets		15 years
Starling MSO Holdings, LLC
Business Acquisition [Line Items]
Cash consideration, subject to purchase price adjustments	$ 284
Purchase price	222
Fair value of equity consideration	62
Intangible assets	126
Goodwill	$ 92