Derivative Financial Instruments (Amounts Reclassified out of AOCI) (Details) - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	$ (658)	$ (498)	$ (97)
Cost of services
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	(8)	(309)	(76)
General and administrative expense
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	(192)	82	18
Sales and marketing expense
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	28	0	0
Research and development expense
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	0	(271)	(39)
Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	$ (486)	$ 0	$ 0