Segment and Geographic Area Information North American, Australian & U.K./European Operations (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($) $ / AUD	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) $ / AUD	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($) $ / £	Dec. 31, 2016 USD ($) region provinces reportable_segment $ / AUD	Dec. 31, 2015 USD ($) $ / AUD	Dec. 31, 2014 USD ($) $ / AUD	Dec. 31, 2016 $ / £	Dec. 31, 2016 $ / €	Dec. 31, 2016 $ / CAD	Dec. 01, 2016 $ / AUD	Dec. 31, 2015 $ / £	Dec. 31, 2015 $ / €	Dec. 31, 2015 $ / CAD	Mar. 25, 2015 $ / £	Dec. 31, 2014 $ / £	Dec. 31, 2014 $ / €	Dec. 31, 2014 $ / CAD
Segment Reporting Information [Line Items]
Number of operating regions | region									10
Number of reportable segments | reportable_segment									3
Restructuring costs									$ 8,182,000	$ 0	$ 0
Foreign Currency Exchange Rate, Translation					0.75			1.51		0.75					0.74				1.49
Freight revenues									1,371,566,000	$ 1,400,547,000	1,251,941,000
Freight-related revenues									536,359,000	502,083,000	290,787,000
All other revenues									93,602,000	97,771,000	96,284,000
OPERATING REVENUES									2,001,527,000	2,000,401,000	1,639,012,000
Operating Income/(Loss)	$ 53,571,000	$ 91,851,000	$ 87,194,000	$ 56,996,000	$ 94,631,000	$ 117,559,000	$ 99,451,000	$ 72,620,000	289,612,000	384,261,000	421,571,000
Depreciation and amortization									205,188,000	188,535,000	157,081,000
Loss on settlement of foreign currency forward purchase contracts									0	(18,686,000)	0
Interest expense, net									74,534,000	66,592,000	54,717,000
Provision for/(benefit from) income taxes									74,395,000	75,894,000	107,107,000
Cash expenditures for additions to Property and equipment, net of grants from outside parties									$ 183,450,000	329,762,000	303,519,000
North American Operations [Member]
Segment Reporting Information [Line Items]
Number of operating regions | provinces									8
Restructuring costs									$ 900,000
Freight revenues									913,619,000	949,028,000	1,008,236,000
Freight-related revenues									258,922,000	227,154,000	214,388,000
All other revenues									64,223,000	65,633,000	82,137,000
OPERATING REVENUES									1,236,764,000	1,241,815,000	1,304,761,000
Operating Income/(Loss)									319,551,000	297,486,000	333,194,000
Depreciation and amortization									147,527,000	141,814,000	127,421,000
Loss on settlement of foreign currency forward purchase contracts										(16,374,000)
Interest expense, net									40,985,000	39,651,000	41,732,000
Provision for/(benefit from) income taxes									80,701,000	69,552,000	86,363,000
Cash expenditures for additions to Property and equipment, net of grants from outside parties									137,334,000	266,548,000	277,725,000
Australian Operations [Member]
Segment Reporting Information [Line Items]
Restructuring costs									800,000
Freight revenues									120,622,000	146,850,000	243,705,000
Freight-related revenues									95,776,000	87,616,000	55,461,000
All other revenues									6,188,000	8,486,000	14,104,000
OPERATING REVENUES									222,586,000	242,952,000	313,270,000
Operating Income/(Loss)									4,810,000	54,842,000	90,396,000
Depreciation and amortization									30,863,000	27,425,000	28,095,000
Loss on settlement of foreign currency forward purchase contracts										(2,312,000)
Interest expense, net									13,958,000	8,976,000	12,152,000
Provision for/(benefit from) income taxes									988,000	12,890,000	23,443,000
Cash expenditures for additions to Property and equipment, net of grants from outside parties									11,285,000	31,179,000	24,930,000
U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Restructuring costs									6,500,000
Freight revenues									337,325,000	304,669,000	0
Freight-related revenues									181,661,000	187,313,000	20,938,000
All other revenues									23,191,000	23,652,000	43,000
OPERATING REVENUES									542,177,000	515,634,000	20,981,000
Operating Income/(Loss)									(34,749,000)	31,933,000	(2,019,000)
Depreciation and amortization									26,798,000	19,296,000	1,565,000
Loss on settlement of foreign currency forward purchase contracts										0
Interest expense, net									19,591,000	17,965,000	833,000
Provision for/(benefit from) income taxes									(7,294,000)	(6,548,000)	(2,699,000)
Cash expenditures for additions to Property and equipment, net of grants from outside parties									$ 34,831,000	$ 32,035,000	$ 864,000
Year to Date Average [Member]
Segment Reporting Information [Line Items]
Foreign Currency Exchange Rate, Translation	0.74				0.75				0.74	0.75	0.90	1.36	1.11	0.76		1.53	1.11	0.78		1.65	1.33	0.91