Fair Value of Financial Assets and Liabilities, Credit Related Contingent Features (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]
Derivative instruments in a gross liability position	$ 0	$ 1,400,000
Payments required if credit ratings were downgraded below investment grade		1,400,000
Collateral posted on derivative instruments	0	0
Collateral posted related to adequate assurance clauses in derivative contracts	$ 0	$ 0

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features for adequate assurance clauses.

No definition available.

+ Details

Name:	psco_CollateralAlreadyPostedAdequateAssuranceClausesAggregateFairValue
Namespace Prefix:	psco_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a gross liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

No definition available.

+ Details

Name:	psco_DerivativeGrossLiabilityPositionAggregateFairValue
Namespace Prefix:	psco_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate fair value of assets needed to immediately settle the derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624258-113959

+ Details

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

- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624258-113959

+ Details

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

- Details

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