Commitment and contingencies (Details) $ in Millions				1 Months Ended		3 Months Ended	6 Months Ended
	Mar. 19, 2024 USD ($)	Nov. 02, 2022 USD ($)	May 05, 2022 USD ($)	Aug. 31, 2022 USD ($)	Dec. 31, 2017 case	Dec. 31, 2020 case	Feb. 29, 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							$ 6,123		$ 6,261
Pending Litigation | Subsequent Event
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							6,100
Estimated litigation liability, current							450
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
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							335
Humana | Settled Litigation
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party							$ 642
Accrued litigation obligations								$ 360