Intangible Assets, Goodwill and Acquisitions - Summary of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2021	Sep. 30, 2021
Goodwill [Line Items]
Beginning balance	$ 1,950.8	$ 1,859.3
Acquisitions	(0.3)	91.5
Ending balance	1,950.5	1,950.8
Maintenance Services
Goodwill [Line Items]
Beginning balance	1,758.0	1,680.4
Acquisitions	1.4	77.6
Ending balance	1,759.4	1,758.0
Development Services
Goodwill [Line Items]
Beginning balance	192.8	178.9
Acquisitions	(1.7)	13.9
Ending balance	$ 191.1	$ 192.8

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=120320667&loc=SL49117168-202975

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant