Summary of Accounting policies - Additional Information (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2019
Disposal Transactions Closing in October 2019 [Abstract]
Number of Disposal Transactions	3
Disposal Transactions Closing October 2019		2
Disposal Transactions Closing November 2019 - January 2020		1

Disposal Transactions Closing November 2019 - January 2020

No definition available.

Name:	cpk_DisposalTransactionsClosingNovember2019January2020
Namespace Prefix:	cpk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration