Pharmhouse - Pharmhouse financial guarantee - Additional information (Details) - CAD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Feb. 23, 2021
Line Of Credit Facility [Line Items]
Financial liabilities	$ 3,201,660				$ 1,679,875				$ 3,201,660	$ 1,679,875
Expected credit loss in net income (loss)	(699,978)	$ (904,380)	$ (32,061)	$ (108,501)	$ (1,303,021)	$ (91,354)	$ 258,918	$ (185,869)	(1,744,920)	$ (1,321,326)	$ (736,281)
Pharmhouse Credit Agreement
Line Of Credit Facility [Line Items]
Non - revolving credit facility, maximum Principle amount												$ 90,000
Expected credit loss	$ (32,500)								(32,500)
Expected credit loss in net income (loss)									$ 32,500