Basis of Presentation and Summary of Significant Accounting Policies - Accounting Standards Update (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by investing activities	$ (13,783)	$ (12,694)	$ 3,337
Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Movements in restricted cash		(24,496)	(24,040)
Accounting Standards Update 2016-18 | As initially reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by investing activities		11,802	27,377
Accounting Standards Update 2016-18 | Change for adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by investing activities		$ (12,694)	$ 3,337