Changes in Operations U.K/Europe Pentalver (Details) £ in Thousands, AUD in Thousands, $ in Thousands						3 Months Ended								12 Months Ended
	May 03, 2017 GBP (£) $ / AUD	May 03, 2017 USD ($)	Dec. 01, 2016 AUD	Dec. 01, 2016 USD ($)	Nov. 01, 2016 USD ($) employee	Dec. 31, 2017 USD ($) employee	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) $ / AUD	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) a employee seaport	Dec. 31, 2016 USD ($) $ / AUD	Dec. 31, 2015 USD ($) $ / AUD	May 03, 2017 USD ($) $ / AUD	Dec. 01, 2016 USD ($)	Dec. 31, 2015 $ / £	Mar. 25, 2015 $ / £
Payments to Acquire Businesses, Net of Cash Acquired														$ 107,586	$ 969,476	$ 740,237
Foreign Currency Exchange Rate, Translation	1.29									0.74					0.74	0.75	1.29		1.51	1.49
Entity Number of Employees | employee						8,000								8,000
Revenues						$ 571,576	$ 576,927	$ 540,433	$ 519,108	$ 516,534	$ 501,002	$ 501,375	$ 482,616
Operating income/(loss)						108,179	$ 111,489	$ 101,340	$ 77,454	53,571	$ 91,851	$ 87,194	$ 56,996	$ 398,462	$ 289,612	$ 384,261
Cost of Services, Depreciation and Amortization														250,457	205,188	$ 188,535
GOODWILL						$ 1,165,587				$ 1,125,596				$ 1,165,587	$ 1,125,596
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life														46 years	48 years
Pentalver Transport Limited [Member]
Business Acquisition, Date of Acquisition Agreement	May 03, 2017	May 03, 2017
Cash consideration	£ 97,800	$ 126,200
Payments to Acquire Businesses, Net of Cash Acquired	77,500	100,100
Cash Acquired from Acquisition	20,200	$ 26,100
Number of Major Seaports | seaport														4
Number of trucks | employee						150								150
Entity Number of Employees | employee						600								600
Revenues														$ 102,600
Operating income/(loss)														4,300
Cost of Services, Depreciation and Amortization														3,300
Business Combination, Integration Related Costs														$ 3,900
Cash and cash equivalents	20,224																$ 26,117
Accounts receivable	16,849																21,759
Materials and supplies	13,360																17,253
Prepaid expenses and other	3,238																4,182
Property and equipment	20,649																26,666
GOODWILL	8,592																11,096
Total assets	124,912																161,312
Accounts payable and accrued expenses	21,341																27,560
Deferred income tax liabilities, net	5,220																6,741
Deferred items-grants from outside parties	601																776
Net assets	£ 97,750																126,235
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	33 years	33 years
Goodwill deductible for tax purposes																	0
Pentalver Transport Limited [Member] | Minimum [Member]
Acres of Land Owned | a														100
Pentalver Transport Limited [Member] | Maximum [Member]
Business Combination, Operational Rights, Terms of Contract, Number of Years	50 years	50 years
Providence and Worcester Railroad [Member]
Cash consideration					$ 126,200
Entity Number of Employees | employee					130
Business Combination, Integration Related Costs														$ 3,100
Cash and cash equivalents					$ 1,529
Accounts receivable					4,011
Materials and supplies					1,048
Prepaid expenses and other					648
Property and equipment					129,473
GOODWILL					27,938
Total assets					164,647
Accounts payable and accrued expenses					9,759
Deferred income tax liabilities, net					27,464
Net assets					$ 126,151
Goodwill deductible for tax purposes																	0
GRail [Member]
Cash consideration			AUD 1,140,000	$ 844,900
Accounts receivable			1,556															$ 1,153
Materials and supplies			411															305
Property and equipment			279,592															207,206
GOODWILL			415,959															308,267
Total assets			1,332,518															987,530
Accounts payable and accrued expenses			5,796															4,296
Deferred income tax liabilities, net			190,551															141,217
Net assets			AUD 1,136,171															$ 842,017
Goodwill deductible for tax purposes																	$ 0
Freightliner [Member]
Number of trucks | employee						200								200
Other Expense [Member] | Pentalver Transport Limited [Member]
Business Combination, Integration Related Costs														$ 3,800
Other Expense [Member] | Providence and Worcester Railroad [Member]
Business Combination, Integration Related Costs														400
Labor and Benefits [Member] | Pentalver Transport Limited [Member]
Business Combination, Integration Related Costs														100
Labor and Benefits [Member] | Providence and Worcester Railroad [Member]
Business Combination, Integration Related Costs														$ 2,700
Operational Network Rights [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life														92 years	100 years
Operational Network Rights [Member] | Pentalver Transport Limited [Member]
Intangible assets	£ 42,000	$ 54,239