Subsequent Event (Details) - USD ($)	Oct. 01, 2018	Nov. 07, 2018	Sep. 30, 2018	Sep. 30, 2017
Secured Revolving Credit Facility
Subsequent Event [Line Items]
Maximum borrowing capacity			$ 200,000,000	$ 180,000,000
Secured Revolving Credit Facility | Maximum
Subsequent Event [Line Items]
Allowed increase in borrowing capacity			$ 250,000,000
Subsequent Event
Subsequent Event [Line Items]
Stock repurchase program authorized amount		$ 50,000,000
Accelerated share repurchases, aggregate purchase price		$ 16,500,000
Subsequent Event | Secured Revolving Credit Facility
Subsequent Event [Line Items]
Basis points	0.50%
Subsequent Event | Secured Revolving Credit Facility | Maximum
Subsequent Event [Line Items]
Allowed increase in borrowing capacity	$ 210,000,000