Segment Reporting - Regional Long-lived Assets By Country (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Long-lived assets	$ 6,114.1	$ 6,310.3
U.S.
Segment Reporting Information [Line Items]
Long-lived assets	3,172.0	3,162.5
U.K.
Segment Reporting Information [Line Items]
Long-lived assets	2,505.9	2,685.3
Other countries
Segment Reporting Information [Line Items]
Long-lived assets	$ 436.2	$ 462.5