Segment Data - Schedule of revenue by geographical areas (Details) - USD ($) $ 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
Revenues from External Customers and Long-Lived Assets [Line Items]
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
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									5,861.5	5,403.6	4,298.7
Australia
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									556.6	589.5	711.3
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									396.2	425.9	364.6
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 1,936.7	$ 1,800.9	$ 1,549.3