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Derivative Instruments - Fair Values of Derivative Contracts Recorded in Consolidated Balance Sheets (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Derivatives, Fair Value [Line Items]    
Energy Marketing Contract Liabilities, Current $ 1,018us-gaap_EnergyMarketingContractLiabilitiesCurrent $ 127us-gaap_EnergyMarketingContractLiabilitiesCurrent
Mark-to-market energy liabilities | Forward Contracts    
Derivatives, Fair Value [Line Items]    
Energy Marketing Contract Liabilities, Current 283us-gaap_EnergyMarketingContractLiabilitiesCurrent
/ us-gaap_BalanceSheetLocationAxis
= cpk_MarkToMarketEnergyLiabilitiesMember
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember		 127us-gaap_EnergyMarketingContractLiabilitiesCurrent
/ us-gaap_BalanceSheetLocationAxis
= cpk_MarkToMarketEnergyLiabilitiesMember
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember
Mark-to-market energy liabilities | Propane Swap Agreement    
Derivatives, Fair Value [Line Items]    
Energy Marketing Contract Liabilities, Current $ 735us-gaap_EnergyMarketingContractLiabilitiesCurrent
/ us-gaap_BalanceSheetLocationAxis
= cpk_MarkToMarketEnergyLiabilitiesMember
/ us-gaap_DerivativeByNatureAxis
= cpk_PropaneSwapAgreementMember		 $ 0us-gaap_EnergyMarketingContractLiabilitiesCurrent
/ us-gaap_BalanceSheetLocationAxis
= cpk_MarkToMarketEnergyLiabilitiesMember
/ us-gaap_DerivativeByNatureAxis
= cpk_PropaneSwapAgreementMember