Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Revenue	$ 2,483.9	$ 2,288.0	$ 4,768.5	$ 4,472.8
Costs and expenses:
Costs of services (exclusive of depreciation and amortization)	2,016.6	1,874.8	3,916.9	3,707.3
Operating, administrative and other	318.3	294.2	624.1	590.2
Depreciation and amortization	26.2	31.2	52.9	63.7
Restructuring, impairment and related charges	0.0	17.4	6.5	22.4
Total costs and expenses	2,361.1	2,217.6	4,600.4	4,383.6
Operating income	122.8	70.4	168.1	89.2
Interest expense, net of interest income	(53.2)	(60.8)	(105.5)	(119.5)
Earnings from equity method investments	0.2	4.3	11.3	16.0
Other income, net	6.4	3.3	7.3	5.0
Earnings (loss) before income taxes	76.2	17.2	81.2	(9.3)
Provision for income taxes	18.9	3.7	22.0	6.0
Net income (loss)	$ 57.3	$ 13.5	$ 59.2	$ (15.3)
Basic earnings (loss) per share:
Earnings (loss) per share attributable to common shareholders, basic (in dollars per share)	$ 0.25	$ 0.06	$ 0.26	$ (0.07)
Weighted average shares outstanding for basic earnings (loss) per share (in shares)	231.4	229.0	230.9	228.5
Diluted earnings (loss) per share:
Earnings (loss) per share attributable to common shareholders, diluted (in dollars per share)	$ 0.25	$ 0.06	$ 0.25	$ (0.07)
Weighted average shares outstanding for diluted earnings (loss) per share (in shares)	232.4	231.5	232.4	228.5