Statements of Consolidated Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Operating Revenue	$ 1,182.3	$ 1,214.5
Operating Expenses:
Salaries, wages and employee benefits	718.2	729.7
Fuel, operating expenses and supplies	235.9	230.2
Purchased transportation	146.3	155.4
Depreciation and amortization	40.0	37.7
Other operating expenses	63.8	62.6
Losses on property disposals, net	1.6	3.2
Impairment charges	8.2	0.0
Total operating expenses	1,214.0	1,218.8
Operating Loss	(31.7)	(4.3)
Nonoperating Expenses:
Interest expense	27.0	25.6
Non-union pension and postretirement benefits	0.3	(0.5)
Other, net	(0.2)	(1.9)
Nonoperating expenses, net	27.1	23.2
Loss before income taxes	(58.8)	(27.5)
Income tax benefit	(9.7)	(12.9)
Net loss	(49.1)	(14.6)
Other comprehensive income, net of tax	3.5	2.0
Comprehensive Loss	$ (45.6)	$ (12.6)
Average Common Shares Outstanding – Basic (in shares)	33,150	32,821
Average Common Shares Outstanding – Diluted (in shares)	33,150	32,821
Basic and Diluted Loss Per Share
Income (loss) Per Share – Basic (in dollars per share)	$ (1.48)	$ (0.44)
Income (loss) Per Share – Diluted (in dollars per share)	$ (1.48)	$ (0.44)