Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2019	Oct. 01, 2018	Sep. 30, 2018
Accounts Receivable, Net, Current [Abstract]
Accounts receivable, net	$ 163,653	$ 163,653	$ 125,200	$ 125,192
Contract with Customer, Asset, Net, Current [Abstract]
Contract assets	$ 4,100	$ 4,100	8,200
Capitalized Contract Cost [Abstract]
Sales commission amortization period	60 months	60 months
Deferred commissions	$ 1,100	$ 1,100	1,500
Deferred commission amortization expense	200	400
Contract with Customer, Liability [Abstract]
Current contract liabilities	31,200	31,200	$ 28,734	$ 25,884
Change in Contract with Customer, Liability [Abstract]
Revenue recognized	$ 11,800	$ 23,900

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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-Publisher FASB
-Name Accounting Standards Codification
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The amount of expense recognized in the current period for the periodic realization of capitalized fees that were paid to salespeople, distributors, brokers, and agents at the time of the conclusion of the sale. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amortization period of cost capitalized in obtaining or fulfilling contract with customer, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer; classified as noncurrent.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

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Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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