Commitment and contingencies (Details) $ in Millions					1 Months Ended		3 Months Ended	9 Months Ended
	Jun. 18, 2024 USD ($)	Mar. 19, 2024 USD ($)	Nov. 02, 2022 USD ($)	May 05, 2022 USD ($)	Aug. 31, 2022 USD ($)	Dec. 31, 2017 case	Dec. 31, 2020 case	May 31, 2024 USD ($)	Dec. 29, 2023 USD ($)	Aug. 31, 2023 USD ($)	Aug. 23, 2023 USD ($)	Jun. 08, 2023	Nov. 30, 2022 USD ($)
Loss Contingencies [Line Items]
Accrued litigation obligations								$ 5,890		$ 6,261
Pending Litigation
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party		$ 988
Estimated litigation liability		79
Damages limit		$ 79
Settlement Frameworks | Pending Litigation
Loss Contingencies [Line Items]
Estimated litigation liability													$ 6,500
Accrued litigation obligations			$ 754
Settlement Frameworks | Settled Litigation
Loss Contingencies [Line Items]
Estimated litigation liability								6,600
Accrued litigation obligations								5,900
Estimated litigation liability, current								744
Litigation Settlement, Percentage Of Litigating Subdivisions												99.50%
Settling States | Pending Litigation
Loss Contingencies [Line Items]
Estimated litigation liability			$ 4,800
Litigation settlement, period			15 years
Settling Tribes | Pending Litigation
Loss Contingencies [Line Items]
Estimated litigation liability			$ 155
Litigation settlement, period			15 years
Consolidated Cases in State of Florida | Settled Litigation
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party				$ 683
Estimated litigation liability					$ 683
Accrued litigation obligations				$ 620
Litigation settlement, period				18 years
Estimated litigation liability, current				$ 63
Ohio Combined Cases | Pending Litigation
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party					$ 651
Loss Contingency, New Claims Filed, Number | case						2
Litigation Settlement, Period					15 years
Ohio Combined Cases | Pending Litigation | Subsequent Event
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party	$ 28
Rite Aid Merger
Loss Contingencies [Line Items]
Loss Contingency, New Claims Filed, Number | case							2
Rite Aid Merger | Pending Litigation
Loss Contingencies [Line Items]
Estimated litigation liability											$ 193
Usual and Customary Pricing | Pending Litigation
Loss Contingencies [Line Items]
Estimated litigation liability								310
Humana | Settled Litigation
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party								$ 642
Accrued litigation obligations									$ 360