Selected Financial Information Regarding the Results of Operations of Charter Fleet Business (Detail) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Income (loss) from discontinued operations, net of tax	$ 1,187	$ (40,030)	$ 6,459	$ (34,308)
Charter Fleet Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	13,404	14,230	33,970	46,812
Loss on disposal of discontinued operations		(27,690)		(27,690)
Income before provision for income taxes	2,004	1,362	6,745	7,766
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax, Total	2,004	(26,328)	6,745	(19,924)
Provision for income taxes	(817)	(240)	(2,286)	(1,759)
Total Income (loss) from discontinued operations, net of tax	$ 1,187	$ (26,568)	$ 4,459	$ (21,683)