Share-Based Compensation Plans - Summary of Stock Activity under DSCP (Parenthetical) (Detail) (Directors Stock Compensation Plan [Member], Chief Executive Officer [Member])	1 Months Ended
Jan. 31, 2011
Directors Stock Compensation Plan [Member] \| Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock awarded	304

Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Awarded To Non Employee Directors

No definition available.

Name:	cpk_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAwardedToNonEmployeeDirectors
Namespace Prefix:	cpk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration