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Financial Instruments - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Average daily tanker rate over remaining duration of charter contract $ 29,139 $ 29,498
Discount rate over remaining duration of contract 8.82% 8.68%
Written down to aggregate estimated fair value $ 800,000  
Impairment of vessels, description No other assets or liabilities were carried at fair value except for the impairment of three vessel asset groups.