Taxes on Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Regulatory-liability-related: ITC and excess deferred taxes	$ 1,049	$ 1,649
Regulatory-liability-related: California Corp Franchise Tax	4,337	3,690
Other nonproperty-related	2,005	2,609
Contributions and advances	8,655	9,443
Deferred tax assets	16,046	17,391
Deferred tax liabilities:
Fixed assets	(131,534)	(121,802)
Regulatory-asset-related: depreciation and other	(21,575)	(21,754)
Other nonproperty-related	(155)	(152)
Balancing and memorandum accounts	(6,663)	(1,020)
Deferred charges	(6,064)	(6,632)
Deferred tax liabilities	(165,991)	(151,360)
Accumulated deferred income taxes - net	(149,945)	(133,969)
Current
Federal	13,741	15,585	9,107
State	5,930	5,273	7,108
Total current tax expense	19,671	20,858	16,215
Deferred
Federal	14,769	13,088	15,189
State	1,343	1,999	(1,328)
Total deferred tax expense	16,112	15,087	13,861
Income tax expense/(benefit)	35,783	35,945	30,076
Reconciliations of the effective tax rates to the federal statutory rate
Federal taxes on pretax income at statutory rate	34,464	31,533	25,230
State income tax, net of federal benefit	5,111	4,957	3,781
Flow-through on fixed assets	646	636	1,026
Flow-through on pension costs	612	10	254
Flow-through on removal costs	(2,141)	(943)	(281)
Domestic production activities deduction	(2,944)	(553)	(277)
Investment tax credit	(91)	(91)	(91)
Other – net	126	396	434
Income tax expense/(benefit)	35,783	35,945	30,076
Pretax income from continuing operations	98,469	90,093	72,086
Effective income tax rate (as a percent)	36.30%	39.90%	41.70%
Tax Authorities
Taxes on income
Net interest receivable	757	2,838	2,364
Recognized interest income	99	473	121
GSWC
Deferred tax assets:
Regulatory-liability-related: ITC and excess deferred taxes	1,049	1,649
Regulatory-liability-related: California Corp Franchise Tax	4,337	3,690
Other nonproperty-related	1,543	2,151
Contributions and advances	8,655	9,443
Deferred tax assets	15,584	16,933
Deferred tax liabilities:
Fixed assets	(131,548)	(121,881)
Regulatory-asset-related: depreciation and other	(21,575)	(21,754)
Other nonproperty-related	(155)	(151)
Balancing and memorandum accounts	(6,663)	(1,020)
Deferred charges	(6,064)	(6,632)
Deferred tax liabilities	(166,005)	(151,438)
Accumulated deferred income taxes - net	(150,421)	(134,505)
Current
Federal	10,768	7,957	5,246
State	6,315	3,830	6,920
Total current tax expense	17,083	11,787	12,166
Deferred
Federal	14,691	12,670	15,118
State	1,360	2,043	(1,313)
Total deferred tax expense	16,051	14,713	13,805
Income tax expense/(benefit)	33,134	26,500	25,971
Reconciliations of the effective tax rates to the federal statutory rate
Federal taxes on pretax income at statutory rate	28,622	23,002	21,278
State income tax, net of federal benefit	5,372	4,048	3,707
Flow-through on fixed assets	646	636	1,026
Flow-through on pension costs	612	10	254
Flow-through on removal costs	(2,141)	(943)	(281)
Domestic production activities deduction	(1,316)	(553)	(277)
Investment tax credit	(91)	(91)	(91)
Other – net	1,430	391	355
Income tax expense/(benefit)	33,134	26,500	25,971
Pretax income from continuing operations	81,776	65,720	60,793
Effective income tax rate (as a percent)	40.50%	40.30%	42.70%
GSWC | Tax Authorities
Taxes on income
Net interest receivable	704	2,775	2,314
Recognized interest income	$ 21	$ 461	$ 102