Statements of Consolidated Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Operating Revenue	$ 1,360.4	$ 1,301.4	$ 4,044.5	$ 3,812.9
Operating Expenses:
Salaries, wages and employee benefits	715.9	729.7	2,163.6	2,204.8
Fuel, operating expenses and supplies	279.3	216.1	810.2	636.6
Purchased transportation	193.0	200.3	584.5	610.6
Depreciation and amortization	36.0	37.8	107.2	106.1
Other operating expenses	88.2	68.9	231.3	205.5
(Gains) losses on property disposals, net	(1.1)	0.2	(9.8)	1.5
Total operating expenses	1,311.3	1,253.0	3,887.0	3,765.1
Operating Income	49.1	48.4	157.5	47.8
Nonoperating Expenses:
Interest expense	41.3	38.6	117.0	112.2
Non-union pension and postretirement benefits	3.7	1.7	2.8	(0.7)
Other, net	(1.6)	(0.2)	(1.5)	(0.5)
Nonoperating expenses, net	43.4	40.1	118.3	111.0
Income (loss) before income taxes	5.7	8.3	39.2	(63.2)
Income tax expense	0.9	0.0	1.9	1.2
Net income (loss)	4.8	8.3	37.3	(64.4)
Other comprehensive loss, net of tax	(17.4)	(28.8)	(13.6)	(21.9)
Comprehensive Income (Loss)	$ (12.6)	$ (20.5)	$ 23.7	$ (86.3)
Average Common Shares Outstanding - Basic	51,448	50,868	51,295	50,661
Average Common Shares Outstanding - Diluted	52,346	51,818	52,217	50,661
Income (loss) per share- Basic	$ 0.09	$ 0.16	$ 0.73	$ (1.27)
Income (Loss) per share- Diluted	$ 0.09	$ 0.16	$ 0.72	$ (1.27)