Restructuring and Related Charges (Location of restructuring amounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 9,149	$ 12,135	$ 12,993
Cost of services
Restructuring Cost and Reserve [Line Items]
Restructuring charges	4,554	8,305	6,257
General and administrative expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3,199	3,053	5,531
Sales and marketing expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	348	305	1,082
Research and development expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	(16)	23	123
Other operating expense, net
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1,064	$ 449	$ 0