Segment Reporting (Geographic Segments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenue	$ 3,615.3	$ 2,875.8
Operating Segments | U.K.
Segment Reporting Information [Line Items]
Revenue	1,635.0	1,496.4
Operating Segments | Belgium
Segment Reporting Information [Line Items]
Revenue	772.7	718.1
Operating Segments | Switzerland
Segment Reporting Information [Line Items]
Revenue	841.8	316.8
Operating Segments | Ireland
Segment Reporting Information [Line Items]
Revenue	135.7	124.2
Operating Segments | Poland
Segment Reporting Information [Line Items]
Revenue	115.6	106.7
Operating Segments | Slovakia
Segment Reporting Information [Line Items]
Revenue	13.0	12.4
Other, including intersegment eliminations
Segment Reporting Information [Line Items]
Revenue	$ 101.5	$ 101.2