Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Accounts Receivable, after Allowance for Credit Loss, Current [Abstract]
Accounts receivable, net	$ 165,176		$ 165,602
Contract with Customer, Asset, Net, Current [Abstract]
Contract assets	$ 17,000		14,000
Capitalized Contract Cost [Abstract]
Sales commission amortization period	60 months
Deferred commissions	$ 700		800
Deferred commission amortization expense	100	$ 200
Contract with Customer, Liability [Abstract]
Current contract liabilities	29,042		29,435
Contract liabilities	29,000		$ 29,400
Revenue recognized	$ 19,100