Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 2,607.5	$ 2,118.8	$ 2,121.7	$ 1,903.0	$ 2,401.9	$ 2,076.0	$ 1,974.3	$ 1,767.7	$ 8,751.0	$ 8,219.9	$ 6,923.9
Operating (loss)/income	123.1	37.0	53.2	(26.0)	43.2	20.6	30.6	(81.9)
Net loss	$ 3.1	$ 11.7	$ 6.3	$ (20.9)	$ (18.0)	$ (41.4)	$ (33.5)	$ (92.9)	$ 0.2	$ (185.8)	$ (221.3)
Net (loss) earnings per share, basic (USD per share)	$ 0.01	$ 0.05	$ 0.03	$ (0.10)	$ (0.09)	$ (0.22)	$ (0.23)	$ (0.64)	$ 0.00	$ (1.09)	$ (1.54)
Net (loss) earnings per share, diluted (USD per share)	$ 0.01	$ 0.05	$ 0.03	$ (0.10)	$ (0.09)	$ (0.22)	$ (0.23)	$ (0.64)	$ 0.00	$ (1.09)	$ (1.54)