Segment Information - Reconciliation of Reportable Segment Assets to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Segment Reporting Information [Line Items]
Cash and cash equivalents, restricted cash, and marketable securities	$ 311,983	$ 305,694
Deferred tax asset	4,765	4,979
Assets	1,614,732	1,559,125
Reportable Segments
Segment Reporting Information [Line Items]
Assets	$ 1,297,984	$ 1,248,452