Segment Data - Schedule of adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting [Abstract]
Net loss	$ (48.7)	$ (78.6)	$ (172.9)	$ (245.6)
Depreciation and amortization	71.6	64.1	213.0	193.0
Interest expense, net of interest income	92.7	49.2	189.1	134.9
Benefit from income taxes	(32.9)	(23.8)	(49.5)	(98.0)
Integration and other costs related to acquisitions	71.5	71.5	178.3	213.3
Pre-IPO stock-based compensation	10.8	6.2	25.7	20.5
Cassidy Turley deferred payment obligation	11.0	10.2	32.3	32.3
Other	3.0	3.4	7.6	11.5
Adjusted EBITDA	$ 179.0	$ 102.2	$ 423.6	$ 261.9