Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Contingency [Line Items]
Income tax expense	$ 1,240	$ 90
Unrecognized tax benefits that would impact effective tax rate	0		$ 4,200
Unrecognized tax benefits, income tax penalties and interest accrued	$ 2,700			$ 2,600
Minimum
Income Tax Contingency [Line Items]
Number of years open for tax examinations	3 years
Maximum
Income Tax Contingency [Line Items]
Number of years open for tax examinations	5 years