Statements of Consolidated Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Operating Revenue	$ 1,256.8	$ 1,303.6	$ 3,711.7	$ 3,844.6
Operating Expenses:
Salaries, wages and employee benefits	756.2	743.0	2,256.7	2,228.7
Fuel, operating expenses and supplies	218.9	233.6	683.1	705.8
Purchased transportation	160.7	183.4	465.0	516.0
Depreciation and amortization	37.2	34.9	115.7	110.2
Other operating expenses	59.0	65.6	180.2	188.8
(Gains) losses on property disposals, net	1.0	1.9	(3.6)	7.3
Impairment charges	0.0	0.0	8.2	0.0
Total operating expenses	1,233.0	1,262.4	3,705.3	3,756.8
Operating Income	23.8	41.2	6.4	87.8
Nonoperating Expenses:
Interest expense	27.9	26.6	83.1	77.7
Loss on extinguishment of debt	11.2	0.0	11.2	0.0
Non-union pension and postretirement benefits	2.0	6.9	2.8	6.0
Other, net	(0.8)	0.1	(0.9)	(0.8)
Nonoperating expenses, net	40.3	33.6	96.2	82.9
Income (loss) before income taxes	(16.5)	7.6	(89.8)	4.9
Income tax expense (benefit)	(0.5)	4.7	(1.1)	2.2
Net income (loss)	(16.0)	2.9	(88.7)	2.7
Other comprehensive income, net of tax	3.6	12.2	9.1	18.5
Comprehensive Income (Loss)	$ (12.4)	$ 15.1	$ (79.6)	$ 21.2
Average Common Shares Outstanding – Basic (in shares)	33,259	33,051	33,098	32,827
Average Common Shares Outstanding – Diluted (in shares)	33,259	33,995	33,098	33,755
Basic and Diluted Loss Per Share
Income (loss) Per Share – Basic (in dollars per share)	$ (0.48)	$ 0.09	$ (2.68)	$ 0.08
Income (loss) Per Share – Diluted (in dollars per share)	$ (0.48)	$ 0.09	$ (2.68)	$ 0.08