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Asset Retirement Obligation - Schedule of Consolidated Balance Sheets where Asset Retirement Obligations Recorded (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2014
Dec. 31, 2013
Mar. 31, 2013
Dec. 31, 2012
Asset retirement obligations $ 4,851 $ 5,032 $ 8,302 $ 8,882
Other Current Liabilities [Member]
       
Asset retirement obligations 1,915 915    
Other Long-Term Liabilities [Member]
       
Asset retirement obligations $ 2,936 $ 4,117