Organizational restructurings - Narrative (Details)			3 Months Ended
	Jun. 17, 2020 employee	Sep. 27, 2019	Jun. 30, 2019	Apr. 02, 2019 seniorOfficer
Restructuring Cost and Reserve [Line Items]
Workforce reduction (positions eliminated) | employee	22
Number of senior officers retired | seniorOfficer				2
Workforce reduction (as a percent)			20.00%
Chief Executive Officer | One-time Termination Benefits
Restructuring Cost and Reserve [Line Items]
Period of COBRA employer contributions		18 months