Applicable margin range percentage above base rate

No definition available.

Name:	cpn_ApplicableMarginRangePercentageAboveBaseRate
Namespace Prefix:	cpn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Applicable margin range percentage added to the British Bankers' Association Interest Settlement Rates

+ References

No definition available.

+ Details

Name:	cpn_ApplicableMarginRangePercentageAboveBritishBankersAssociationInterestSettlementRates
Namespace Prefix:	cpn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Future Line of Credit Facility Maximum Borrowing Capacity

+ References

No definition available.

+ Details

Name:	cpn_FutureLineofCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Incremental Revolving Facilities

+ References

No definition available.

+ Details

Name:	cpn_IncrementalRevolvingFacilities
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Interest periods for LIBOR rate borrowings

+ References

No definition available.

+ Details

Name:	cpn_InterestPeriodsForLiborRateBorrowings
Namespace Prefix:	cpn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease Assets, Accumulated Depreciation

+ References

No definition available.

+ Details

Name:	cpn_LeaseAssetsAccumulatedDepreciation
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lease Assets, Historical Cost

+ References

No definition available.

+ Details

Name:	cpn_LeaseAssetsHistoricalCost
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Letter of Credit Total

+ References

No definition available.

+ Details

Name:	cpn_LetterOfCreditTotal
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum Remaining Lease Term

+ References

No definition available.

+ Details

Name:	cpn_MaximumRemainingLeaseTerm
Namespace Prefix:	cpn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Repayment time for drawings under letters of credit

+ References

No definition available.

+ Details

Name:	cpn_RepaymentTimeForDrawingsUnderLettersOfCredit
Namespace Prefix:	cpn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Total Letter of Credit Sublimit

+ References

No definition available.

+ Details

Name:	cpn_TotalLetterofCreditSublimit
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=114001942&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114001942&loc=d3e12317-112629

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

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

- Definition

Amount of increase (decrease) of the credit facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=cpn_New2023FirstLienTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=cpn_CdhiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=cpn_A2026FirstLienNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpn_InterestPeriodsAxis=cpn_OneMonthMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpn_InterestPeriodsAxis=cpn_TwoMonthsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpn_InterestPeriodsAxis=cpn_ThreeMonthsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpn_InterestPeriodsAxis=cpn_SixMonthsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpn_InterestPeriodsAxis=cpn_NineMonthsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cpn_InterestPeriodsAxis=cpn_TwelveMonthsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=cpn_PrimeRateorTheEurodollarRateForAOneMonthInterestPeriodMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=cpn_FederalFundsEffectiveRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=cpn_EurodollarRateForAOneMonthInterestPeriodMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=cpn_CdhiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=cpn_OtherCorporateFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cpn_GoldmanSachsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cpn_CitiBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=cpn_ShortTermCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=cpn_AmendmentNo.8Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cpn_AmendmentNo.7Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cpn_AmendmentNo.8Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cpn_AmendmentNo.6Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt (Textuals) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
Debt (Textuals) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 11, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Maximum Remaining Lease Term			33 years
Lease Assets, Historical Cost			$ 715	$ 737
Lease Assets, Accumulated Depreciation			353	349
Gains (Losses) on Extinguishment of Debt			$ 28	(38)	$ (25)
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Repayment time for drawings under letters of credit			2 days
Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Applicable margin range percentage above base rate			1.00%
Applicable Margin Range Percentage Above British Bankers' Association Interest Settlement Rates			2.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.25%
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Applicable margin range percentage above base rate			1.25%
Applicable Margin Range Percentage Above British Bankers' Association Interest Settlement Rates			2.25%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.50%
New 2023 First Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 562
CDHI [Member]
Debt Instrument [Line Items]
Letter of Credit Total			$ 300
2026 First Lien Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 625		560
One Month [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest periods for LIBOR rate borrowings			1 month
Two Months [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest periods for LIBOR rate borrowings			2 months
Three Months [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest periods for LIBOR rate borrowings			3 months
Six Months [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest periods for LIBOR rate borrowings			6 months
Nine Months [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest periods for LIBOR rate borrowings			9 months
Twelve Months [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest periods for LIBOR rate borrowings			12 months
Prime Rate Or The Eurodollar Rate For a One Month Interest Period [Member] \| New 2023 First Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.00%
Federal Funds Effective Rate [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate			0.50%
Federal Funds Effective Rate [Member] \| New 2023 First Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.50%
Eurodollar Rate For A One-Month Interest Period [Member] \| New 2023 First Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.00%
CDHI [Member]
Debt Instrument [Line Items]
Future Line of Credit Facility Maximum Borrowing Capacity			$ 125
Other Corporate Facilities [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			200
Other Corporate Facilities [Member] \| Goldman Sachs [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			150
Other Corporate Facilities [Member] \| Citi Bank [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 50
Short Term Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity						$ 300
Amendment No. 8 [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Increase (Decrease), Net	$ 220
Revolving Credit Facility [Member] \| Amendment No. 7 [Member]
Debt Instrument [Line Items]
Total Letter of Credit Sublimit							$ 1,300
Incremental Revolving Facilities							500
Revolving Credit Facility [Member] \| Amendment No. 8 [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,690
Revolving Credit Facility [Member] \| Amendment No. 6 [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,470
Total Letter of Credit Sublimit							$ 1,150
Future Line of Credit Facility Maximum Borrowing Capacity				$ 1,300