Restructuring and Related Charges (Location of restructuring amounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 12,135	$ 12,993	$ 10,422
Cost of services
Restructuring Cost and Reserve [Line Items]
Restructuring charges	8,305	6,257	3,897
General and administrative expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3,053	5,531	4,775
Sales and marketing expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	305	1,082	908
Research and development expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	23	123	606
Other operating expense, net
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 449	$ 0	$ 236