Income Taxes - Tax valuation allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Tax valuation allowance
Deferred tax asset valuation allowance	$ 69,098	$ 81,838
Change in valuation allowance	12,700
Net tax benefit before offset by amounts recorded through OCI	10,000
Deferred tax liability	41,397	$ 8,604
Foreign
Tax valuation allowance
Deferred tax liability	$ 1,000