Income Taxes - Tax valuation allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Tax valuation allowance
Deferred tax asset valuation allowance	$ 58,837	$ 47,887
Change in valuation allowance	11,000
Net tax benefit before offset by amounts recorded through OCI	12,700
Deferred tax liability	37,464	$ 36,157
Foreign
Tax valuation allowance
Deferred tax liability	$ 11,900