v3.19.1

Debt Senior Unsecured Notes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term Debt	$ 10,682		$ 10,156
Gain (Loss) on Extinguishment of Debt	4	$ 0
Senior Unsecured Notes 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt	1,228		1,227
Senior Unsecured Notes 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt	589		599
Senior Unsecured Notes 2025 [Member]
Debt Instrument [Line Items]
Long-term Debt	1,172		1,210
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount, Cumulative	438
Debt Instrument, Repurchased Face Amount	48
Long-term Debt	2,989		$ 3,036
Debt Instrument, Repurchase Amount	44
Gain (Loss) on Extinguishment of Debt	4
Debt Instrument, Repurchase Amount, Cumulative	$ 399

X

- Definition

Debt Instrument, Repurchase Amount, Cumulative

+ References

No definition available.

+ Details

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

X

- Definition

Debt Instrument, Repurchased Face Amount, Cumulative

+ References

No definition available.

+ Details

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

X

- 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

X

- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

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

X

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

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

X

- 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

X

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: 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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

X

- Details

Name:	us-gaap_LongtermDebtTypeAxis=cpn_SeniorUnsecuredNotes2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LongtermDebtTypeAxis=cpn_SeniorUnsecuredNotes2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LongtermDebtTypeAxis=cpn_SeniorUnsecuredNotes2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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