Carrying Values of Major Classes of Assets and Liabilities Held for Sale Included in Consolidated Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total current assets held for sale	$ 3,197	$ 10,161
Total long-term assets held for sale	55,571	77,150
Charter Fleet Business | Assets Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash		1,426
Accounts receivable-net		5,253
Other assets	3,197	3,482
Total current assets held for sale	3,197	10,161
Property, plant and equipment-net	45,892	68,595
Other assets	9,679	8,555
Total long-term assets held for sale	55,571	77,150
Accounts payable and accrued liabilities		8,748
Other liabilities		12,154
Total liabilities associated with assets held for sale		$ 20,902