Regulatory Matters (Details 6) (GSWC, USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Regulatory matters:
Total	$ 176,015	$ 179,957
Low income rate assistance balancing accounts
Regulatory matters:
Discount percentage for qualified low-income water customers	15.00%
Discount percentage for qualified low-income electric customers	20.00%
Commercial paper, term	90 days
Total	$ 9,119	$ 6,194

The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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