Rate Matters (Details) - USD ($) $ in Millions		3 Months Ended
Apr. 29, 2016	Mar. 31, 2016
CPUC Proceeding - Annual Electric Earnings Test
Rate Matters [Abstract]
Public Utilities, Return On Equity Threshold For Earnings Sharing For 2015 Through 2017		9.83%
Subsequent Event \| 2015 Electric Earnings Test
Rate Matters [Abstract]
Public Utilities, Refund to Customers Due to Annual Earnings Test	$ 14.9

The return on equity used as a threshold in the public utility's annual earnings test for 2012-2014, as approved by a regulatory agency. Earnings exceeding this threshold are shared between customers and shareholders.

No definition available.

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Namespace Prefix:	psco_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration