Segment and Geographic Information - Summary of Revenue and Profit Attributable to Our Operating Segments (Parenthetical) (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Revenue Reconciling Item [Line Items]
Depreciation and amortization	$ 80,817	$ 77,824	$ 87,408
Unallocated
Segment Reporting Revenue Reconciling Item [Line Items]
Depreciation and amortization	19,400	20,600	22,700
Software Products \| Operating Segments
Segment Reporting Revenue Reconciling Item [Line Items]
Depreciation and amortization	4,200	4,600	5,100
Professional Services \| Operating Segments
Segment Reporting Revenue Reconciling Item [Line Items]
Depreciation and amortization	$ 1,100	$ 1,400	$ 1,600

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Name:	us-gaap_DepreciationDepletionAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration