Open-Top Hoppers - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014 Railcar
Long Lived Assets Held-for-sale [Line Items]
Number of cars held for disposal	126
Proceeds received from disposal of car	$ 250
Rail cars [Member]
Long Lived Assets Held-for-sale [Line Items]
Anticipated proceeds from disposal of cars	950
Proceeds received from disposal of car	250
Deferred grant income and other revenue	62
Gain on disposal of cars	106
Number of cars sold	25
Number of cars to be disposed of	101
Number of open-top hoppers acquired from GATX	75
Acquisition of open-top hoppers	$ 1,500