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Derivative Instruments - Additional Information (Detail)
12 Months Ended 12 Months Ended
Dec. 31, 2012
USD ($)
Dec. 31, 2011
USD ($)
Dec. 31, 2010
USD ($)
Dec. 31, 2012
Norwegian Kroner denominated bonds due May 2017 [Member]
NOK
May 31, 2012
Norwegian Kroner denominated bonds due May 2017 [Member]
NOK
Dec. 31, 2012
Cross currency swap agreement [Member]
USD ($)
Derivative [Line Items]            
Senior unsecured bond issued       700,000,000 700,000,000  
Derivative fair value liabilities, net   600,000        
Derivative fair value assets, net 1,100,000          
Unrealized losses on derivatives (8,923,000) 10,221,000 26,700,000     (2,700,000)
Realized gains on derivatives           $ 300,000