Derivative Instruments - Additional Information (Detail) gal in Thousands, Mcf in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018 USD ($) $ / gal gal Mcf	Dec. 31, 2017 USD ($) gal
Derivative [Line Items]
Accounts Receivable Subject to Master Netting Arrangement	$ 2,092	$ 2,391
Derivative, Nonmonetary Notional Amount, Volume \| Mcf	100
Energy Marketing Contracts Assets, Current	$ 208	$ 1,286
Volume settled on hedges \| gal		20
Energy Marketing Contract Liabilities, Current	(2,359)	$ (6,247)
Accounts Payable Subject To Master Netting Arrangement	2,092	2,391
Hedging Liability [Member] \| Natural Gas Futures [Member]
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current	(1,639)	(469)
Hedging Liability [Member] \| Natural Gas Swaps [Member]
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current	(404)	(2)
Designated as Hedging Instrument [Member] \| Mark To Market Energy Assets [Member] \| Propane Swap Agreement [Member]
Derivative [Line Items]
Energy Marketing Contracts Assets, Current	204
Energy Marketing Contract Liabilities, Current	(16)	0
Not Designated as Hedging Instrument [Member] \| Mark To Market Energy Assets [Member] \| Propane Swap Agreement [Member]
Derivative [Line Items]
Energy Marketing Contracts Assets, Current	4	13
Not Designated as Hedging Instrument [Member] \| Mark-to-market energy liabilities [Member] \| Natural Gas Futures [Member]
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current	$ (300)	$ (5,776)
PESCO [Member] \| Natural Gas Futures [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| Mcf	22,900
2017 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	2,100
2017 [Member] \| Natural Gas Swaps [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| Mcf	702
2017 [Member] \| Propane Swap Agreement [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal		7,700
Derivative, Cash Received on Hedge	$ 3
2017 [Member] \| Strike Price 4 [Member] \| Propane Swap Agreement [Member]
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements \| $ / gal	0.5900
2018 [Member] \| Propane Swap Agreement [Member]
Derivative [Line Items]
Derivative, Cash Received on Hedge	$ 464
Gross [Member]
Derivative [Line Items]
Accounts Receivable Subject to Master Netting Arrangement	6,555	$ 8,283
Accounts Payable Subject To Master Netting Arrangement	13,912	16,643
Net [Member]
Derivative [Line Items]
Accounts Receivable Subject to Master Netting Arrangement	4,463	5,892
Accounts Payable Subject To Master Netting Arrangement	$ 11,820	$ 14,252

Accounts Payable Subject To Master Netting Arrangement

No definition available.

Name:	cpk_AccountsPayableSubjectToMasterNettingArrangement
Namespace Prefix:	cpk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Accounts Receivable Subject to Master Netting Arrangement

+ References

No definition available.

+ Details

Name:	cpk_AccountsReceivableSubjecttoMasterNettingArrangement
Namespace Prefix:	cpk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Strike Price Per Gallon For The Propane Swap Agreements

+ References

No definition available.

+ Details

Name:	cpk_StrikePricePerGallonForThePropaneSwapAgreements
Namespace Prefix:	cpk_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

Volume settled on hedges

+ References

No definition available.

+ Details

Name:	cpk_Volumesettledonhedges
Namespace Prefix:	cpk_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of cash received during the period on settlement of a hedge.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeCashReceivedOnHedge
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Current liabilities attributable to energy marketing activities (trading activities). Current energy marketing (trading activities) are when entities engage in both financial and physical trading to increase profits, manage their commodity price risk and enhance system reliability. They may trade electricity, coal, natural gas and oil. These entities typically use a variety of financial instruments, including forward contracts, options and swaps.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_EnergyMarketingContractLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of the asset arising from energy trading activities that involves the purchase and sale of energy under forward contracts at fixed and variable prices and the buying and selling of financial energy contracts that include exchange futures and options and over the counter options and swaps, which are expected to be converted into cash or otherwise disposed of within a year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_EnergyMarketingContractsAssetsCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_BalanceSheetLocationAxis=cpk_HedgingLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cpk_NaturalGasFuturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cpk_NaturalGasSwapsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=cpk_MarkToMarketEnergyAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cpk_PropaneSwapAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=cpk_MarkToMarketEnergyLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cpk_PESCOMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpk_OriginationYearAxis=cpk_A2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpk_StrikePricesPropaneSwapAgreementsAxis=cpk_StrikePrice1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpk_OriginationYearAxis=cpk_A2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpk_GrossorNetAxis=cpk_GrossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpk_GrossorNetAxis=cpk_NetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: