Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	$ 7,116	$ 10,585
2020 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	7,000		$ 30,600
2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred		10,600		$ 23,400
Impairment on right-of-use asset		$ 8,700
Employee Severance and Related Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	6,300
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2021	22,051
Costs incurred	6,452
Cash disbursements	(7,000)
Translation adjustments and other	(395)
Balance as of March 31, 2021	21,108		$ 21,108
Software Charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	$ 700