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CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Statement Of Income And Comprehensive Income [Abstract]    
Unrealized hedging gains, income tax benefit   $ 161crk_OtherComprehensiveIncomeUnrealizedHedgingGainsLossesNetOfTaxTaxAmount
Net change in fair value of marketable securities, income tax benefit $ 2,380crk_OtherComprehensiveIncomeNetUnrealizedGainsLossesOnMarketableSecuritiesNetOfTaxTaxAmount $ 8,487crk_OtherComprehensiveIncomeNetUnrealizedGainsLossesOnMarketableSecuritiesNetOfTaxTaxAmount