Restructuring costs - Rollforward of restructuring liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring liability
Accrued costs	$ 3,393	$ 8,505	$ 8,775	$ 12,254
Employee Separation and other
Restructuring liability
Balance as of the beginning of the period			2,000
Accrued costs			7,000
Cash payments			(8,300)
Balance as of the end of the period	700		700
Consulting Costs
Restructuring liability
Balance as of the beginning of the period			800
Accrued costs			1,800
Cash payments			(2,200)
Balance as of the end of the period	$ 400		$ 400