Statements of Consolidated Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Operating Revenue	$ 1,158.6	$ 1,260.4
Operating Expenses:
Salaries, wages and employee benefits	672.5	711.0
Fuel, operating expenses and supplies	240.6	243.6
Purchased transportation	152.0	185.4
Depreciation and amortization	35.3	35.7
Other operating expenses	68.0	81.0
Gains on property disposals, net	(0.5)	(5.5)
Total operating expenses	1,167.9	1,251.2
Operating Income (Loss)	(9.3)	9.2
Nonoperating Expenses:
Interest expense	46.5	37.7
Non-union pension and postretirement benefits	1.2	(0.4)
Other, net	(0.2)	0.2
Nonoperating expenses, net	47.5	37.5
Loss before income taxes	(56.8)	(28.3)
Income tax benefit	(2.2)	(0.8)
Net Loss	(54.6)	(27.5)
Other comprehensive income (loss), net of tax	(2.6)	2.3
Comprehensive Loss	$ (57.2)	$ (25.2)
Average Common Shares Outstanding - Basic	51,729	51,091
Average Common Shares Outstanding - Diluted	51,729	51,091
Loss Per Share - Basic	$ (1.06)	$ (0.54)
Loss Per Share - Diluted	$ (1.06)	$ (0.54)