Revenue Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 682.4	$ 656.4	$ 1,321.0	$ 1,265.9
ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		656.4		1,265.9
Freight Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues	653.1		1,264.5
Freight Revenues [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		629.4		1,216.1
Chemical and Petroleum [Member]
Disaggregation of Revenue [Line Items]
Revenues	157.8		297.5
Chemical and Petroleum [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		138.8		265.3
Chemicals [Member]
Disaggregation of Revenue [Line Items]
Revenues	60.4		118.1
Chemicals [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		56.0		110.6
Petroleum [Member]
Disaggregation of Revenue [Line Items]
Revenues	57.8		106.8
Petroleum [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		50.8		89.6
Plastics [Member]
Disaggregation of Revenue [Line Items]
Revenues	39.6		72.6
Plastics [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		32.0		65.1
Industrial and Consumer Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	152.7		299.0
Industrial and Consumer Products [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		148.6		288.7
Forest Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	69.2		134.5
Forest Products [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		62.2		125.7
Metals and Scrap [Member]
Disaggregation of Revenue [Line Items]
Revenues	54.0		107.8
Metals and Scrap [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		57.3		111.6
Other Industrial and Consumer Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	29.5		56.7
Other Industrial and Consumer Products [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		29.1		51.4
Agriculture and Minerals [Member]
Disaggregation of Revenue [Line Items]
Revenues	125.1		238.5
Agriculture and Minerals [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		123.4		239.7
Grain [Member]
Disaggregation of Revenue [Line Items]
Revenues	75.4		140.6
Grain [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		73.1		139.3
Food Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	36.3		72.5
Food Products [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		38.1		76.4
Ores and Minerals [Member]
Disaggregation of Revenue [Line Items]
Revenues	5.8		10.7
Ores and Minerals [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		4.8		9.1
Stone, Clay and Glass [Member]
Disaggregation of Revenue [Line Items]
Revenues	7.6		14.7
Stone, Clay and Glass [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		7.4		14.9
Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues	56.5		117.8
Energy [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		70.5		139.5
Utility Coal [Member]
Disaggregation of Revenue [Line Items]
Revenues	23.9		53.2
Utility Coal [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		39.0		81.8
Coal and Petroleum Coke [Member]
Disaggregation of Revenue [Line Items]
Revenues	11.2		21.4
Coal and Petroleum Coke [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		10.3		21.3
Frac Sand [Member]
Disaggregation of Revenue [Line Items]
Revenues	10.5		21.6
Frac Sand [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		14.0		24.7
Crude Oil [Member]
Disaggregation of Revenue [Line Items]
Revenues	10.9		21.6
Crude Oil [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		7.2		11.7
Intermodal [Member]
Disaggregation of Revenue [Line Items]
Revenues	93.7		184.6
Intermodal [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		90.6		174.1
Automotive [Member]
Disaggregation of Revenue [Line Items]
Revenues	67.3		127.1
Automotive [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		57.5		108.8
Other Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 29.3		$ 56.5
Other Revenue [Member] | ASC 605 [Member]
Disaggregation of Revenue [Line Items]
Revenues		$ 27.0		$ 49.8