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Lease Obligations - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Disclosure Lease Obligations Additional Information [Abstract]      
Rent expense related to operating leases $ 1,800,000us-gaap_OperatingLeasesRentExpenseNet $ 1,600,000us-gaap_OperatingLeasesRentExpenseNet $ 1,400,000us-gaap_OperatingLeasesRentExpenseNet
Operating Leases, Future Minimum Payments Due, Next Twelve Months 1,100,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent    
Operating Leases, Future Minimum Payments, Due in Two Years 942,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears    
Operating Leases, Future Minimum Payments, Due in Three Years 338,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears    
Operating Leases, Future Minimum Payments, Due in Four Years 293,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears    
Operating Leases, Future Minimum Payments, Due in Five Years 228,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears    
Future minimum payments under current lease agreements, thereafter 2,300,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter    
Future minimum payments under current lease agreements, total 5,200,000us-gaap_OperatingLeasesFutureMinimumPaymentsDue    
Payments to Acquire Capital Leases 1,100,000cpk_PaymentstoAcquireCapitalLeases    
Capital Leases, Future Minimum Payments Due, Next Twelve Months 1,500,000us-gaap_CapitalLeasesFutureMinimumPaymentsDueCurrent    
Capital Leases, Future Minimum Payments Due in Five Years 625,000us-gaap_CapitalLeasesFutureMinimumPaymentsDueInFiveYears    
Capital Leases, Future Minimum Payments Due $ 6,600,000us-gaap_CapitalLeasesFutureMinimumPaymentsDue