Revenue - Unearned Revenue (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2019 USD ($)
Unearned Revenue [Roll Forward]
Unearned revenue, beginning of period	$ 3,933	[1]
Billings	43,071
Revenue recognized	(41,979)
Unearned revenue, end of period	$ 5,025

[1] Prior period information has been restated for the adoption of ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”, which we adopted on October 1, 2018.