Changes in Operations U.K/Europe Freightliner (Details) £ in Thousands, $ in Thousands	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) locomotive rail_car employee	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) locomotive rail_car $ / AUD	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 GBP (£) $ / £	Mar. 31, 2015 USD ($) $ / £	Dec. 31, 2015 USD ($) locomotive rail_car $ / AUD	Dec. 31, 2016 USD ($) locomotive rail_car employee	Dec. 31, 2015 USD ($) locomotive rail_car $ / AUD	Dec. 31, 2014 USD ($) locomotive rail_car	Dec. 01, 2016 $ / AUD	Mar. 25, 2015 GBP (£) locomotive rail_car employee $ / £	Mar. 25, 2015 USD ($) locomotive rail_car employee $ / £
Number of employees | employee	7,300										7,300
Leased locomotives | locomotive	309				333					333	309	333	162
Leased railcars | rail_car	20,738				21,819					21,819	20,738	21,819	18,583
Foreign Currency Exchange Rate, Translation					0.75			1.51	1.51	0.75		0.75		0.74	1.49	1.49
Revenues	$ 516,534	$ 501,002	$ 501,375	$ 482,616	$ 514,853	$ 546,299	$ 542,219		$ 397,030
Operating Income	$ 53,571	$ 91,851	$ 87,194	$ 56,996	$ 94,631	$ 117,559	$ 99,451		$ 72,620		$ 289,612	$ 384,261	$ 421,571
Loss on settlement of foreign currency forward purchase contracts											$ 0	18,686	$ 0
Freightliner [Member]
Business Acquisition, Effective Date of Acquisition								Mar. 25, 2015	Mar. 25, 2015
Business Acquisition, Name of Acquired Entity								Freightliner Group Limited (Freightliner)	Freightliner Group Limited (Freightliner)
Percentage of economic interest retained by acquiree's management								6.00%	6.00%
Number of employees | employee															2,500	2,500
Leased locomotives | locomotive															250	250
Electric locomotives | locomotive															45	45
Leased railcars | rail_car															5,500	5,500
Cash consideration								£ 492,083	$ 733,006
Deferred consideration								24,200	36,048
Total consideration								£ 516,283	$ 769,054
Business Combination, Contingent Consideration, Liability, Noncurrent															£ 24,200	$ 36,000
Revenues										$ 531,300
Operating Income										$ 33,400
Business Combination, Acquisition Related Costs												12,600
Business Combination, Integration Related Costs												2,600
Loss on settlement of foreign currency forward purchase contracts												$ 18,700