Changes in Operations United States P&W (Details) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Nov. 01, 2016 USD ($) mile employee port locomotive carload $ / shares	Dec. 31, 2016 USD ($) employee	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) employee	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Revenues		$ 516,534	$ 501,002	$ 501,375	$ 482,616	$ 514,853	$ 546,299	$ 542,219	$ 397,030
Operating Income/(Loss)		$ 53,571	$ 91,851	$ 87,194	$ 56,996	94,631	$ 117,559	$ 99,451	$ 72,620	$ 289,612	$ 384,261	$ 421,571
Entity Number of Employees | employee		7,300								7,300
Goodwill		$ 1,125,596				$ 826,575				$ 1,125,596	$ 826,575	$ 628,815
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
Revenues										5,200
Operating Income/(Loss)										(300)
Business Combination, Acquisition Related Costs										$ 2,000
Entity Number of Employees | employee	140
Entity Number of Locomotives Owned or Leased | locomotive	32
Track Miles Owned | mile	163
Track Miles Leased | mile	350
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	127,020
Goodwill	26,969
Total Assets	161,225
Accounts payable and accrued expenses	8,505
Deferred income tax liabilities, net	26,569
Net assets	$ 126,151