Segment Information Segment Information - Revenue by Geography (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,217.2	$ 1,285.1	$ 1,447.6
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	543.8	611.4	743.9
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 673.4	$ 673.7	$ 703.7