Statements of Consolidated Operations - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Operating Revenue	$ 5,121.8	$ 4,513.7	$ 4,871.2
Operating Expenses:
Salaries, wages and employee benefits	2,921.7	2,770.1	2,963.7
Fuel, operating expenses and supplies	858.1	719.1	889.0
Purchased transportation	800.2	638.8	614.2
Depreciation and amortization	143.6	134.9	152.4
Other operating expenses	293.9	239.6	241.2
(Gains) losses on property disposals, net	0.7	(45.3)	(13.7)
Impairment charges	0.0	0.0	8.2
Total operating expenses	5,018.2	4,457.2	4,855.0
Operating Income	103.6	56.5	16.2
Nonoperating Expenses:
Interest expense	150.7	135.9	111.2
Non-union pension and postretirement benefits	59.3	(6.3)	3.1
Loss on extinguishment of debt	0.0	0.0	11.2
Other, net	(0.4)	0.0	(1.0)
Nonoperating expenses, net	209.6	129.6	124.5
Loss before income taxes	(106.0)	(73.1)	(108.3)
Income tax expense (benefit)	3.1	(19.6)	(4.3)
Net Loss	$ (109.1)	$ (53.5)	$ (104.0)
Average common shares outstanding - Basic	50,720	41,694	33,252
Average common shares outstanding - Diluted	50,720	41,694	33,252
Earnings (Loss) Per Share - Basic	$ (2.15)	$ (1.28)	$ (3.13)
Earnings (Loss) Per Share - Diluted	$ (2.15)	$ (1.28)	$ (3.13)