Restructuring and Related Charges (Location of restructuring amounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 12,993	$ 10,422	$ 31,665
Cost of services
Restructuring Cost and Reserve [Line Items]
Restructuring charges	6,257	3,897	14,574
General and administrative expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	5,531	4,775	7,877
Sales and marketing expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,082	908	8,727
Research and development expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	123	606	487
Other operating (income) expense, net
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 236	$ 0