Commitments and Contingencies (Details) $ in Millions	1 Months Ended				2 Months Ended
	Oct. 31, 2018 USD ($)	Dec. 31, 2017 item	Sep. 30, 2015 pharmacy	Feb. 28, 2006 lawsuit item director	Sep. 30, 2017 complaint	Sep. 30, 2018 item store
Loss contingencies
Number of store leases guaranteed | store						84
Number of material accruals for outstanding legal matters						0
Number of pharmacies indicated in subpoena | pharmacy			8
Omnicare, Inc.
Loss contingencies
New claims filed, number | lawsuit				2
Number of officers named in lawsuit				3
Number of directors named in lawsuit | director				2
Indiana State District Council of Laborers and HOD Carriers Pension and Wellfare Fund
Loss contingencies
Litigation settlement, amount | $	$ 20
National Opioid Litigation | Maximum
Loss contingencies
the number of relevant federal court cases that named the company		100
Shareholder Matters
Loss contingencies
Number of complaints | complaint					4
Number of complaints filed in Rhode Island | complaint					3