Basis of Presentation - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue from External Customer [Line Items]
Operating Revenue	$ 1,301.4	$ 1,183.4	$ 3,812.9	$ 3,349.2
LTL revenue
Revenue from External Customer [Line Items]
Operating Revenue	1,170.5	1,073.0	3,436.8	3,044.2
Other revenue
Revenue from External Customer [Line Items]
Operating Revenue	$ 130.9	$ 110.4	$ 376.1	$ 305.0