Income Taxes - Tax valuation allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Tax valuation allowance
Deferred tax asset valuation allowance	$ 81,839	$ 57,106
Change in valuation allowance	24,700
Net tax benefit before offset by amounts recorded through OCI	21,100
Deferred tax liability	8,330	$ 28,647
Foreign
Tax valuation allowance
Deferred tax liability	$ 700