Restructuring and other related costs - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2019 store employee	Mar. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Number of stores closed | store	22
Gain (loss) on termination of lease | $		$ 1.9
Accelerated lease cost, gross | $		$ 16.1
Retail Store Employees
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee	170
Corporate Employees
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee	5