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Summary of Accounting Policies Stock Dividend (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Mar. 31, 2015
Summary Of Accounting Policies [Line Items]    
Stock Split in Form of Stock Dividend Adjustment to Retained Earnings $ 9cpk_StockSplitinFormofStockDividendAdjustmenttoRetainedEarnings  
Common Stock, Par or Stated Value Per Share $ 0.4867us-gaap_CommonStockParOrStatedValuePerShare $ 0.4867us-gaap_CommonStockParOrStatedValuePerShare
Common Stock [Member]    
Summary Of Accounting Policies [Line Items]    
Stock Split in Form of Stock Dividend Adjustment to Retained Earnings $ (2,365)cpk_StockSplitinFormofStockDividendAdjustmenttoRetainedEarnings
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember