Variable Interest Entities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Mar. 31, 2012 Tranche	Aug. 31, 2012 Vehicle	May 31, 2012 Vehicle
Variable Interest Entity [Line Items]
Ownership interest in VIE	1.00%
Third party Ownership interest	99.00%
Number of Rail Cars Sold		743	743
Operating leases	$ 115.4
Number of operating leases tranches	3
Target rate of return		8.0
Agreement Expiration Time		2033-03
Value of railcars		61.1
Description of Deferred revenue		This $4.2 million, which is held in restricted cash, was recorded as a reduction in revenue on the sale of 600 new railcars and a reduction in gain on sale on the sale of the 143 used railcars with a credit to deferred revenue.
Intangible and Other Assets
Variable Interest Entity [Line Items]
Carrying amounts		0.6
Maximum
Variable Interest Entity [Line Items]
Maximum potential obligation		$ 4.2	4.2
Property Subject to Operating Lease
Variable Interest Entity [Line Items]
Number of Rail Cars Sold	1,363
First Tranche
Variable Interest Entity [Line Items]
Transaction closing date	May 2012
Third Tranche
Variable Interest Entity [Line Items]
Transaction closing date	March 2013