Changes in Operations Freightliner (Details) £ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($) $ / £	Mar. 31, 2015 GBP (£)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($) $ / £	Sep. 30, 2015 USD ($) $ / £	Sep. 30, 2015 USD ($) $ / £	Sep. 30, 2014 USD ($) $ / £	Mar. 25, 2015 GBP (£) rail_car employee locomotive $ / £	Mar. 25, 2015 USD ($) rail_car employee locomotive $ / £	Jun. 30, 2014 $ / £	Mar. 31, 2014 $ / £
Foreign currency exchange rate | $ / £	1.51			1.67	1.51	1.51	1.67	1.49	1.49	1.68	1.66
Freightliner income from operations contributed since acquisition date	$ 117,559,000			$ 123,116,000		$ 289,630,000	$ 308,100,000
Loss on settlement of foreign currency forward purchase contracts	0			$ 0		(18,686,000)	$ 0
Freightliner [Member]
Business Acquisition, Effective Date of Acquisition		Mar. 25, 2015	Mar. 25, 2015
Outstanding share capital acquired								100.00%	100.00%
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%
Cash consideration		£ 492,083	$ 733,006,000
Deferred consideration		23,957	35,687,000
Total consideration		£ 516,040	$ 768,693,000
Contingent liability								£ 24,000	$ 35,700,000
Change in estimated fair value of deferred consideration						0
Change in contingent consideration liability						0
Leased locomotives | locomotive								250	250
Electric locomotives | locomotive								45	45
Railcars | rail_car								5,500	5,500
Number of employees | employee								2,500	2,500
Freightliner revenues contributed since acquisition date					$ 363,500,000
Acquisition and integration costs	$ 700,000					14,000,000
Loss on settlement of foreign currency forward purchase contracts						$ (18,700,000)