Acquisition, Dispositions and Atlantic Restructuring Charges - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended		1 Months Ended	6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2013	Jun. 30, 2013 Maximum Forecasted	Jun. 30, 2013 Minimum Forecasted	Jun. 30, 2013 Charter Fleet Business	Jun. 30, 2012 Charter Fleet Business	Dec. 31, 2011 Charter Fleet Business	Mar. 19, 2012 Charter Fleet Business Vessel	Mar. 19, 2012 Secunda International Limited Vessel	Jun. 30, 2013 Multi Function Support Vessel Vessel
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total purchase consideration			$ 9,000,000
Purchase consideration - cash			6,000,000
Purchase consideration - restricted shares			313,580
Number of vessels held for sale											4
Proceeds from sale of discontinued assets		32,000,000
Gain on sale of the Bold Endurance		12,500,000
Number of vessels operated									10
Number of vessels										14
Cash Proceeds from sale of business						61,000,000
Gain on sale						300,000	257,000
Write-down of charter fleet business								22,000,000
Expected restructuring cost				60,000,000	45,000,000
Restructuring cost incurred	$ 15,500,000