Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to decrease accumulated deficit	$ (562,972)	$ (571,207)
Operating lease obligations	$ 4,300
Average discount rate, remaining rental payments	4.00%
Accounting Standards Update 2016-18 [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash and cash equivalents	$ 400	$ 1,000	$ 400
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to decrease accumulated deficit	200
Minimum [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for adoption of accounting standard	1,800
Maximum [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment for adoption of accounting standard	$ 2,800