Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 1,931.6	$ 2,118.8	$ 5,570.6	$ 6,143.5
Costs and expenses:
Cost of services (exclusive of depreciation and amortization)	1,599.6	1,692.2	4,652.3	4,944.1
Operating, administrative and other	254.3	315.2	810.4	908.9
Depreciation and amortization	64.9	75.0	211.5	222.8
Restructuring, impairment and related charges	13.1	(0.6)	45.0	3.5
Total costs and expenses	1,931.9	2,081.8	5,719.2	6,079.3
Operating income (loss)	(0.3)	37.0	(148.6)	64.2
Interest expense, net of interest income	(44.9)	(37.4)	(120.2)	(112.8)
Earnings from equity method investments	2.8	0.7	5.8	2.0
Other income, net	0.5	0.4	31.0	3.2
Earnings (loss) before income taxes	(41.9)	0.7	(232.0)	(43.4)
Benefit from income taxes	(4.6)	(11.0)	(38.8)	(40.5)
Net income (loss)	$ (37.3)	$ 11.7	$ (193.2)	$ (2.9)
Basic earnings (loss) per share:
Earnings (loss) per share attributable to common shareholders, basic (in dollars per share)	$ (0.17)	$ 0.05	$ (0.88)	$ (0.01)
Weighted average shares outstanding for basic earnings (loss) per share	221.1	218.0	220.5	217.2
Diluted earnings (loss) per share:
Earnings (loss) per share attributable to common shareholders, diluted (in dollars per share)	$ (0.17)	$ 0.05	$ (0.88)	$ (0.01)
Weighted average shares outstanding for diluted earnings (loss) per share	221.1	224.5	220.5	217.2