Changes in Operations Freightliner (Details)	3 Months Ended			0 Months Ended	3 Months Ended
	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 25, 2015 USD ($)	Mar. 31, 2015 Freightliner [Member] USD ($)	Mar. 31, 2015 Freightliner [Member] USD ($)	Mar. 31, 2015 Freightliner [Member] GBP (£)	Mar. 25, 2015 Freightliner [Member] USD ($) rail_car employee locomotive	Mar. 25, 2015 Freightliner [Member] GBP (£)
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%
Foreign currency exchange rate	1.51	1.66	1.49
Cash consideration					$ 733,006,000	£ 492,083,000
Deferred consideration					35,687,000	23,957,000
Total consideration					768,693,000	516,040,000
Contingent liability							35,700,000	24,000,000
Leased locomotives							250	250
Wagons leased							5,500	5,500
Number of employees							2,500	2,500
Revenues from Freightliner included within operating revenues				15,100,000
Freightliner operating expenses included within operating expenses	13,999,000	0		14,000,000
Acquisition-related costs					12,600,000
Loss on settlement of foreign currency forward purchase contracts	$ (18,686,000)	$ 0			$ (18,700,000)