Segment Information - Reconciliation of Reportable Segment Assets to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Cash and cash equivalents, restricted cash, and marketable securities	$ 286,310	$ 305,694
Deferred tax asset	4,447	4,979
Assets	1,763,255	1,559,125
Operating Segments
Segment Reporting Information [Line Items]
Assets	$ 1,472,498	$ 1,248,452