Discontinued Operation - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of charter fleet business	$ 61,000,000
Gain on disposal of discontinued operations	257,000
Charter Fleet Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal of discontinued operations	$ 257,000	[1]
Number of vessels	10
Secunda International Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of vessels	14

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