Summary of Significant Accounting Policies - Summary of Property and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment	$ 614.7	$ 605.5
Land
Property, Plant and Equipment [Line Items]
Property and equipment	0.5	0.5
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment	7.1	10.2
Furniture, Fixtures, and Autos
Property, Plant and Equipment [Line Items]
Property and equipment	167.1	164.8
Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	133.8	130.3
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 306.2	$ 299.7