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Share-Based Compensation - Share-Based Compensation Amounts Included in Net Income (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total compensation expense $ 537us-gaap_AllocatedShareBasedCompensationExpense $ 638us-gaap_AllocatedShareBasedCompensationExpense
Less: tax benefit (217)us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense (257)us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Share-Based Compensation amounts included in net income 320us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax 381us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax
Awards to non-employee directors [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total compensation expense 150us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_PlanNameAxis
= cpk_AwardstononemployeedirectorsMember		 124us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_PlanNameAxis
= cpk_AwardstononemployeedirectorsMember
Award to key employees [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total compensation expense $ 387us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_PlanNameAxis
= cpk_AwardtokeyemployeesMember		 $ 514us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_PlanNameAxis
= cpk_AwardtokeyemployeesMember