Basis of Presentation - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue from External Customer [Line Items]
Operating Revenue	$ 1,198.4	$ 1,150.4
LTL revenue
Revenue from External Customer [Line Items]
Operating Revenue	1,083.5	1,050.7
Other revenue
Revenue from External Customer [Line Items]
Operating Revenue	$ 114.9	$ 99.7