Segment Information Segments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) reportable_segment provinces region	Mar. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of operating regions | region	10
Number of reportable segments | reportable_segment	3
Freight revenues	$ 377,745	$ 326,414
Freight-related revenues	119,337	133,458
All other revenues	22,026	22,744
Total Operating revenues	519,108	482,616
Operating income/(loss)	77,454	56,996
Depreciation and amortization	60,774	49,330
Interest expense, net	26,138	17,900
Provision for/(benefit from) income taxes	21,928	12,808
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	$ 29,967	31,683
North American Operations [Member]
Segment Reporting Information [Line Items]
Number of operating regions | provinces	8
Freight revenues	$ 238,281	221,825
Freight-related revenues	65,345	61,525
All other revenues	15,850	16,428
Total Operating revenues	319,476	299,778
Operating income/(loss)	67,570	69,978
Depreciation and amortization	38,867	36,189
Interest expense, net	10,551	10,465
Provision for/(benefit from) income taxes	22,074	16,009
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	24,215	25,416
Australian Operations [Member]
Segment Reporting Information [Line Items]
Freight revenues	60,874	24,777
Freight-related revenues	11,709	25,490
All other revenues	1,324	1,531
Total Operating revenues	73,907	51,798
Operating income/(loss)	17,159	(11,751)
Depreciation and amortization	15,192	6,656
Interest expense, net	13,987	2,395
Provision for/(benefit from) income taxes	861	(2,525)
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	1,462	867
U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Freight revenues	78,590	79,812
Freight-related revenues	42,283	46,443
All other revenues	4,852	4,785
Total Operating revenues	125,725	131,040
Operating income/(loss)	(7,275)	(1,231)
Depreciation and amortization	6,715	6,485
Interest expense, net	1,600	5,040
Provision for/(benefit from) income taxes	(1,007)	(676)
Expenditures for Additions to Property and Equipment Net of Grants From Outside Parties	$ 4,290	$ 5,400