Selected Financial Information Regarding Results of Operations of Charter Fleet Business (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total income from discontinued operations, net of tax	$ 1,187	$ 3,497		$ 6,459
Charter Fleet Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	13,404	8,184	[1]	33,970	[2]
Income before provision for income taxes	2,004	3,497	[1]	6,745	[2]
Provision for income taxes	(817)			(2,286)	[2]
Total income from discontinued operations, net of tax	$ 1,187	$ 3,497	[1]	$ 4,459	[2]

[1] Includes the charter fleet operations through March 19, 2012.

[2] Amounts presented exclude a $2.0 million recovery of an environmental reserve associated with our 2006 sale of Talleres Navales del Golfo, S.A. de C.V.