Acquisitions - Narrative (Details) - USD ($) $ in Millions					3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 25, 2023	Nov. 10, 2022	Oct. 11, 2022	Apr. 18, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Business Acquisition [Line Items]
Business Combination, Cash Aquired							$ 3.1
Services revenue					$ 460.7	$ 404.4	1,328.2	$ 1,135.2
Other Intangible Assets
Business Acquisition [Line Items]
Acquired intangible assets at purchasing price				$ 1.8
Roker Inc. (Roker)
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Jul. 25, 2023
Business Combination, Cash Aquired	$ 3.1
Business Acquisition, Goodwill, Expected Tax Deductible Amount					0.9		0.9
Acquired intangible assets at purchasing price							2.3
Roker Inc. (Roker) | Other Intangible Assets
Business Acquisition [Line Items]
Services revenue					0.1		0.1
Loss before income taxes					0.1		0.1
Acquired intangible assets at purchasing price							2.3
KMP Associates Limited (KMP)
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Oct. 11, 2022
Business Combination, Consideration Transferred, Total			$ 13.8
Business Combination, Cash Aquired			0.9
Business Combination, Assumption Debt			$ 0.3
Divrt, Inc. (Divrt)
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition		Nov. 10, 2022
Business Combination, Consideration Transferred, Total		$ 17.6
Maximum Amount Of Contingent Consideration To Former Owner		7.0
Contingent consideration payable to former owner					1.4		1.4
Accrued In Projected Contingent Consideration		$ 4.0
Estimated Potential Payout					4.4		4.4		$ 4.1
Operating expense					0.1		0.3
Kmp Associates Limited and Divrt Inc [Member]
Business Acquisition [Line Items]
Acquired intangible assets at purchasing price							23.5		$ 23.5
Kmp Associates Limited and Divrt Inc [Member] | Other Intangible Assets
Business Acquisition [Line Items]
Services revenue					1.5		4.7
Loss before income taxes					$ 0.9		$ 2.6