Revenue (Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Contract assets	$ 80,759	$ 73,467	$ 69,147
Cumulative effect of adoption of new accounting standards	0	6,106
Recognized in current period	347,660	325,289
Reclassified to accounts receivable	(342,371)	(302,055)
Contract with Customer, Asset, increase (decrease) for contract divested in sale of business	2,710	(13,025)
Foreign currency	(707)	217
Contract liabilities	26,259	39,051	$ 17,652
Cumulative effect of adoption of new accounting standards	0	1,773
Recognized in current period	322,595	319,722
Amounts in beginning balance reclassified to revenue	(39,100)	(20,754)
Current period amounts reclassified to revenue	(295,085)	(276,002)
Contract with Customer, Liability, increase (decrease) for contract divested in sale of business	(700)	(1,302)
Foreign currency	$ (502)	$ (2,038)