Segment Information - Reconciliation of Reportable Segment Assets to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Cash, cash equivalents and marketable securities	$ 140,059	$ 251,226
Deferred tax assets	28,012	43,798
Assets	1,487,877	1,095,257
Discontinued Operations, Held-for-sale
Segment Reporting Information [Line Items]
Assets held for sale	128,077	125,200
Operating Segments
Segment Reporting Information [Line Items]
Assets	$ 1,191,729	$ 675,033