Carrying Values of Major Classes of Assets and Liabilities to Charter Fleet Business that are Included in Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other current assets		$ 3,197
Property, plant and equipment-net		45,892
Other long-term assets		9,679
Total long-term assets held for sale	$ 26,758	$ 55,571