Contract Balances and Performance Obligations - Contract Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Revenue from Contract with Customer [Abstract]
Contract with Customer, Liability, Current	$ 111,000	$ 103,300
Contract with Customer, Liability	116,320	108,118	$ 114,729
Contract with Customer, Liability, Revenue Recognized	(93,265)	(83,125)
Contract With Customer, Liability, Excluding Revenue Recognized	101,467	76,514
Contract with Customer, Liability, Noncurrent	$ 5,300	$ 4,800