Segments - Summary of Certain Financial Data For Each of Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net service revenues		$ 570.7	$ 526.0
Adjusted EBITDA	[1]	51.7	50.1
Capital expenditures		14.5	17.3
Net (loss)		(12.6)	(8.8)
Interest expense		17.4	17.1
Income tax (benefit)		(4.9)	(3.2)
Depreciation expense		20.2	19.3
Amortization expense		13.5	15.1
Establish public company financial reporting compliance	[2]	0.9	0.4
Business transformation and integration costs	[3]	8.3	4.3
Offering-related expenses	[4]	0.4
Equity-based compensation	[5]	8.5	5.9
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA	[1]	(15.1)	(15.6)
Capital expenditures		0.8	3.0
Operating Segments | Maintenance Services
Segment Reporting Information [Line Items]
Net service revenues		418.9	392.5
Adjusted EBITDA	[1]	47.7	48.7
Capital expenditures		11.7	11.1
Operating Segments | Development Services
Segment Reporting Information [Line Items]
Net service revenues		152.8	134.4
Adjusted EBITDA	[1]	19.1	17.0
Capital expenditures		2.0	3.2
Eliminations
Segment Reporting Information [Line Items]
Net service revenues		$ (1.0)	$ (0.9)

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

[2] Represents costs incurred to establish public company financial reporting compliance, including costs to comply with the requirements of Sarbanes-Oxley and the accelerated adoption of the revenue recognition standard (ASC 606 – Revenue from Contracts with Customers) and other miscellaneous costs.

[3] Business transformation and integration costs consist of (i) severance and related costs; (ii) rebranding of vehicle fleet; (iii) business integration costs and (iv) information technology infrastructure transformation costs and other.

[4] Represents expenses incurred for IPO related litigation and subsequent registration statements. No related expenses were incurred during the three months ended December 31, 2018.

[5] Represents equity-based compensation expense and related taxes recognized for equity incentive plans outstanding, including $2.0 of equity based compensation expense related to the IPO during the three months ended December 31, 2019.