Segments - Summary of Certain Financial Data For Each of Segments (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Net Service Revenues		$ 738.8	$ 766.0	$ 2,038.4	$ 2,072.3
Adjusted EBITDA	[1]	107.9	101.8	219.5	197.1
Capital Expenditures		23.2	15.2	46.0	57.9
Net income (loss)		23.5	16.8	40.8	(24.1)
Interest expense		15.1	27.4	48.2	78.3
Income tax expense (benefit)		9.9	7.6	17.5	(5.5)
Depreciation expense		28.1	26.4	79.8	80.9
Amortization expense		8.6	10.8	27.4	33.7
Business transformation and integration costs	[2]	17.1	8.9	33.9	17.5
Gain on divestiture	[3]	(0.1)	0.0	(44.0)	0.0
Equity-based compensation	[4]	5.1	3.9	15.3	15.9
C O V I D19 Related Expenses	[5]	0.0	0.0	0.0	0.4
Debt extinguishment	[6]	0.6	0.0	0.6	0.0
Severance and related costs		4.3	4.1	10.5	6.0
Business integration	[7]	0.4	2.8	(0.5)	5.3
IT infrastructure, transformation, and other	[8]	12.4	2.0	23.9	6.2
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA		(12.5)	(16.3)	(43.4)	(52.7)
Capital Expenditures		2.0	3.4	3.9	4.7
Operating Segments | Maintenance Services
Segment Reporting Information [Line Items]
Net Service Revenues		524.7	564.6	1,477.5	1,545.7
Adjusted EBITDA		89.3	94.0	197.8	196.2
Capital Expenditures		15.4	9.3	31.9	46.0
Operating Segments | Development Services
Segment Reporting Information [Line Items]
Net Service Revenues		215.0	203.4	564.8	533.3
Adjusted EBITDA		31.1	24.1	65.1	53.6
Capital Expenditures		5.8	2.5	10.2	7.2
Eliminations
Segment Reporting Information [Line Items]
Net Service Revenues		$ (0.9)	$ (2.0)	$ (3.9)	$ (6.7)

[1] Presented below is a reconciliation of Net income (loss) to Adjusted EBITDA:

[2] Business transformation and integration costs consist of (i) severance and related costs; (ii) business integration costs and (iii) information technology infrastructure, transformation, and other costs.

[3] Represents the realized gain on sale and transaction related expenses from the divestiture of U.S. Lawns on January 12, 2024

[4] Represents equity-based compensation expense and related taxes recognized for equity incentive plans outstanding.

[5] Represents expenses related to the Company’s response to the COVID-19 pandemic, principally temporary and incremental salary and related expenses, personal protective equipment, cleaning and supply purchases, and other.

[6] Represents losses on the extinguishment of debt related to Amendment No. 8 to the Credit Agreement and includes the write-off of deferred finance fees and original issue discount.

[7] Represents isolated expenses specifically related to the integration of acquired companies such as one-time employee retention costs, employee onboarding and training costs, fleet and uniform rebranding costs, and adjustments to performance based contingent consideration. The Company excludes Business integration costs from the measures disclosed above since such expenses vary in amount due to the number of acquisitions and size of acquired companies as well as factors specific to each acquisition, and as a result lack predictability as to occurrence and/or timing, and create a lack of comparability between periods.

[8] Represents expenses related to distinct initiatives, typically significant enterprise-wide changes. Such expenses are excluded from the measures disclosed above since such expenses vary in amount based on occurrence as well as factors specific to each of the activities, are outside of the normal operations of the business, and create a lack of comparability between periods.