Commitments and Contingencies, Legal Contingencies (Details) - PSCo [Member] - Line Extension Disputes	1 Months Ended	3 Months Ended
Dec. 31, 2015	Mar. 31, 2017
Legal Contingencies [Abstract]
Loss Contingency, Number of Plaintiffs		2
Minimum [Member]
Legal Contingencies [Abstract]
Loss Contingency, Number of Plaintiffs	50

Number of plaintiffs that have filed claims pertaining to a loss contingency.

No definition available.

Name:	us-gaap_LossContingencyNumberOfPlaintiffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration