Fair Value Measurements (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Assets:
Cash and cash equivalents	$ 68,359	$ 97,720
Short-term investments	26,829
Restricted cash	24,851
Deferred compensation	6,442	5,773
Liabilities:
Deferred compensation	4,991	4,449
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	68,359	97,720
Short-term investments	26,829
Restricted cash	24,851
Deferred compensation	0	0
Liabilities:
Deferred compensation	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Short-term investments	0
Restricted cash	0
Deferred compensation	6,442	5,773
Liabilities:
Deferred compensation	4,991	4,449
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Short-term investments	0
Restricted cash	0
Deferred compensation	0	0
Liabilities:
Deferred compensation	$ 0	$ 0