Taxes on Income (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Taxes on income
Unrecognized Tax Benefits	$ 0
Interest Expense	21,992,000	$ 21,088,000	$ 21,617,000
Deferred tax assets:
Regulatory-liability-related: ITC and excess deferred taxes	903,000	952,000
Regulatory-liability-related: California Corp Franchise Tax	3,365,000	4,530,000
Other nonproperty-related	1,993,000	2,486,000
Contributions and advances	7,464,000	8,026,000
Deferred tax assets	13,725,000	15,994,000
Deferred tax liabilities:
Fixed assets	(200,378,000)	(178,004,000)
Regulatory-asset-related: depreciation and other	(24,402,000)	(21,658,000)
Deferred Tax Liabilities, Regulatory Assets and Liabilities Related to State Franchise Tax	(2,033,000)	(2,440,000)
Other nonproperty-related	0	(66,000)
Balancing and memorandum accounts	(7,010,000)	(1,824,000)
Deferred charges	(4,429,000)	(4,849,000)
Deferred tax liabilities	(238,252,000)	(208,841,000)
Accumulated deferred income taxes - net	(224,527,000)	(192,847,000)
Current
Federal	2,297,000	21,866,000	5,595,000
State	4,798,000	5,442,000	137,000
Total current tax expense	7,095,000	27,308,000	5,732,000
Deferred
Federal	26,715,000	8,948,000	24,815,000
State	925,000	1,475,000	7,501,000
Total deferred tax expense	27,640,000	10,423,000	32,316,000
Reconciliations of the effective tax rates to the federal statutory rate
Federal taxes on pretax income at statutory rate	33,067,000	34,375,000	34,687,000
Flow-through on removal costs	(78,000)	(1,560,000)	(643,000)
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount	(83,000)	(88,000)	(91,000)
Income tax expense/(benefit)	34,735,000	37,731,000	38,048,000
Pretax income from continuing operations	$ 94,478,000	$ 98,215,000	$ 99,106,000
Effective income tax rate (as a percent)	36.80%	38.40%	38.40%
Increase (decrease) in taxes resulting from:	$ 3,029,000	$ 4,843,000	$ 4,781,000
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation, Amount	994,000	626,000	651,000
Income Tax Reconciliation Flow Through on Pension Costs	(247,000)	267,000	(507,000)
Income Tax Reconciliation Cost of Removal	(2,068,000)	(929,000)	(1,571,000)
Income Tax Examination, Penalties Accrued	0	0	0
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	121,000	197,000	741,000
Income Tax Examination, Penalties Expense	0	0	0
Tax Authorities
Taxes on income
Net interest receivable	461,000	504,000	504,000
Recognized interest income		0
Consolidated Entities [Member] | Tax Authorities
Taxes on income
Recognized interest income	8,000		19,000
AWR Parent
Reconciliations of the effective tax rates to the federal statutory rate
Income tax expense/(benefit)	(546,000)	(810,000)	(996,000)
Pretax income from continuing operations	59,197,000	59,674,000	60,062,000
GSWC
Taxes on income
Interest Expense	21,782,000	20,998,000	21,524,000
Deferred tax assets:
Regulatory-liability-related: ITC and excess deferred taxes	903,000	952,000
Regulatory-liability-related: California Corp Franchise Tax	3,365,000	4,530,000
Other nonproperty-related	1,901,000	1,997,000
Contributions and advances	7,712,000	8,026,000
Deferred tax assets	13,881,000	15,505,000
Deferred tax liabilities:
Fixed assets	(203,133,000)	(179,660,000)
Regulatory-asset-related: depreciation and other	(24,402,000)	(21,658,000)
Deferred Tax Liabilities, Regulatory Assets and Liabilities Related to State Franchise Tax	(2,208,000)	(3,051,000)
Other nonproperty-related	(68,000)	(65,000)
Balancing and memorandum accounts	(7,271,000)	(1,824,000)
Deferred charges	(4,597,000)	(4,905,000)
Deferred tax liabilities	(241,679,000)	(211,163,000)
Accumulated deferred income taxes - net	(227,798,000)	(195,658,000)
Current
Federal	(3,115,000)	16,196,000	408,000
State	3,625,000	5,557,000	(2,754,000)
Total current tax expense	510,000	21,753,000	(2,346,000)
Deferred
Federal	25,864,000	8,536,000	24,373,000
State	2,235,000	2,183,000	9,979,000
Total deferred tax expense	28,099,000	10,719,000	34,352,000
Reconciliations of the effective tax rates to the federal statutory rate
Federal taxes on pretax income at statutory rate	26,452,000	28,022,000	27,952,000
Flow-through on removal costs	0	(1,268,000)	(55,000)
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount	(82,000)	(88,000)	(91,000)
Income tax expense/(benefit)	28,609,000	32,472,000	32,006,000
Pretax income from continuing operations	$ 75,578,000	$ 80,063,000	$ 79,863,000
Effective income tax rate (as a percent)	37.90%	40.60%	40.10%
Increase (decrease) in taxes resulting from:	$ 3,118,000	$ 5,151,000	$ 4,693,000
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation, Amount	994,000	626,000	651,000
Income Tax Reconciliation Flow Through on Pension Costs	(247,000)	267,000	(507,000)
Income Tax Reconciliation Cost of Removal	(2,068,000)	(929,000)	(1,571,000)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	442,000	691,000	934,000
GSWC | Tax Authorities
Taxes on income
Net interest receivable	499,000	512,000	472,000
Interest Expense		$ 3,000
Recognized interest income	$ 7,000		14,000
Tax Year 2013 [Member]
Taxes on income
Deferred Tax Liabilities Related to Repair-And-Maintenance Deductions			$ 30,800,000