Changes in Operations United States P&W (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Nov. 01, 2016 USD ($) mile employee locomotive $ / shares	Dec. 31, 2017 USD ($) employee port carload	May 03, 2017 USD ($)	Dec. 31, 2016 USD ($)
Entity Number of Employees | employee		8,000
Goodwill		$ 1,165,587		$ 1,125,596
Providence and Worcester Railroad [Member]
Business Acquisition, Effective Date of Acquisition	Nov. 01, 2016
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Business Acquisition, Share Price | $ / shares	$ 25.00
Cash consideration	$ 126,200
Business Combination, Integration Related Costs		$ 3,100
Entity Number of Employees | employee	130
Entity Number of Locomotives Owned or Leased | locomotive	32
Track Miles Owned | mile	229
Track Miles Leased | mile	300
Annual carloads transported | carload		44,000
Number of Ports With Provided Rail Service | port		3
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
Other long-term liabilities	1,273
Net assets	$ 126,151
Goodwill deductible for tax purposes			$ 0
Labor and Benefits [Member] | Providence and Worcester Railroad [Member]
Business Combination, Integration Related Costs		$ 2,700
Other Expense [Member] | Providence and Worcester Railroad [Member]
Business Combination, Integration Related Costs		$ 400