Commitments and contingencies (Details) $ in Millions	3 Months Ended	12 Months Ended
	Nov. 30, 2018 lawsuit	Aug. 31, 2018 USD ($)	Dec. 20, 2018 lawsuit
Loss Contingencies [Line Items]
Payments for legal settlements | $		$ 34.5
Delaware Court of Chancery
Loss Contingencies [Line Items]
Lawsuits filed and dismissed	8
Subsequent Event | Rite Aid Transactions
Loss Contingencies [Line Items]
Number of lawsuits filed			2
Subsequent Event | State of Pennsylvania in the Court of Common Pleas of Cumberland County
Loss Contingencies [Line Items]
Number of lawsuits filed			1
Subsequent Event | Middle District of Pennsylvania
Loss Contingencies [Line Items]
Number of lawsuits filed			1