Income Taxes Summary of Income Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Tax cuts and jobs act of 2017, change in tax rate, deferred tax liability, income tax (expense) benefit		$ 3,641
Domestic	$ 81,276	(9,140)	$ (8,613)
Foreign	40,490	10,256	17,879
Income before income taxes	$ 121,766	$ 1,116	$ 9,266