CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Utility plant:
Utility plant	$ 1,960,381	$ 1,843,766
Less accumulated depreciation and amortization	(579,262)	(549,469)
Net utility plant	1,381,119	1,294,297
Current assets:
Cash and cash equivalents	27,203	42,277	9,866	13,869
Receivables	71,588	59,908
Other current assets	15,097	24,025
Total current assets	113,888	126,210
Other assets:
Regulatory assets	319,898	229,577
Other assets	39,682	41,982
Total other assets	359,580	271,559
Total assets	1,854,587	1,692,066
Capitalization:
Common stockholders' equity	449,829	435,526	420,634	402,949
Long-term debt, less current maturities	481,632	479,181
Total capitalization	931,461	914,707
Current liabilities:
Current maturities of long-term debt	6,533	2,380
Short-term borrowings	47,140	23,750
Accounts payable	51,578	42,530
Accrued expenses and other liabilities	46,624	38,688
Total current liabilities	151,875	107,348
Unamortized investment tax credits	2,254	2,244
Deferred income taxes, net	116,368	107,084
Pension and postretirement benefits other than pension	232,110	155,224
Regulatory and other liabilities	79,050	82,204
Advances for construction	187,278	186,899
Contributions in aid of construction	154,191	136,356
Total capitalization and liabilities	1,854,587	1,692,066
Parent Company
Utility plant:
Utility plant	324	324
Less accumulated depreciation and amortization	(51)
Net utility plant	273	324
Current assets:
Cash and cash equivalents	89	188	532	427
Receivables	158
Receivables from affiliates	7,817	3,478
Other current assets		181
Total current assets	8,064	3,847
Other assets:
Investments in affiliates	466,515	434,322
Long-term affiliate notes receivable	28,921	34,517
Other assets	1,144	848
Total other assets	496,580	469,687
Total assets	504,917	473,858
Capitalization:
Common stockholders' equity	449,829	435,527
Affiliate long-term debt	7,832	9,808
Total capitalization	457,661	445,335
Current liabilities:
Short-term borrowings	47,140	23,750
Payables to affiliates	52	5,265
Accrued expenses and other liabilities	625	67
Total current liabilities	47,817	29,082
Deferred income taxes, net	(561)	(559)
Total capitalization and liabilities	504,917	473,858
Cal Water
Utility plant:
Utility plant	1,808,568	1,710,213
Less accumulated depreciation and amortization	(551,345)	(522,486)
Net utility plant	1,257,223	1,187,727
Current assets:
Cash and cash equivalents	18,475	40,446	6,000	3,025
Receivables	76,227	56,068
Receivables from affiliates	3,446	4,907
Other current assets	14,225	22,842
Total current assets	112,373	124,263
Other assets:
Regulatory assets	317,564	227,440
Long-term affiliate notes receivable	7,832	7,880
Other assets	31,662	34,153
Total other assets	357,058	269,473
Total assets	1,726,654	1,581,463
Capitalization:
Common stockholders' equity	417,810	402,402
Long-term debt, less current maturities	477,998	475,030
Total capitalization	895,808	877,432
Current liabilities:
Current maturities of long-term debt	5,851	1,709
Payables to affiliates	190	56
Accounts payable	47,568	38,204
Accrued expenses and other liabilities	46,462	34,444
Total current liabilities	100,071	74,413
Unamortized investment tax credits	2,254	2,244
Deferred income taxes, net	113,925	105,786
Pension and postretirement benefits other than pension	232,110	155,224
Regulatory and other liabilities	71,034	74,057
Advances for construction	185,902	185,332
Contributions in aid of construction	125,550	106,975
Total capitalization and liabilities	1,726,654	1,581,463
All Other Subsidiaries
Utility plant:
Utility plant	158,688	140,428
Less accumulated depreciation and amortization	(29,251)	(28,244)
Net utility plant	129,437	112,184
Current assets:
Cash and cash equivalents	8,639	1,643	3,334	10,417
Receivables	(4,797)	3,840
Receivables from affiliates	5	3,621
Other current assets	872	1,002
Total current assets	4,719	10,106
Other assets:
Regulatory assets	2,334	2,137
Long-term affiliate notes receivable		1,928
Other assets	7,081	7,186
Total other assets	9,415	11,251
Total assets	143,571	133,541
Capitalization:
Common stockholders' equity	54,377	37,611
Affiliate long-term debt	28,921	34,517
Long-term debt, less current maturities	3,634	4,151
Total capitalization	86,932	76,279
Current liabilities:
Current maturities of long-term debt	682	671
Payables to affiliates	11,026	6,685
Accounts payable	4,010	4,326
Accrued expenses and other liabilities	(547)	4,145
Total current liabilities	15,171	15,827
Deferred income taxes, net	3,435	2,340
Regulatory and other liabilities	8,016	8,147
Advances for construction	1,376	1,567
Contributions in aid of construction	28,641	29,381
Total capitalization and liabilities	143,571	133,541
Consolidating Adjustments
Utility plant:
Utility plant	(7,199)	(7,199)
Less accumulated depreciation and amortization	1,385	1,261
Net utility plant	(5,814)	(5,938)
Current assets:
Receivables from affiliates	(11,268)	(12,006)
Total current assets	(11,268)	(12,006)
Other assets:
Investments in affiliates	(466,515)	(434,322)
Long-term affiliate notes receivable	(36,753)	(44,325)
Other assets	(205)	(205)
Total other assets	(503,473)	(478,852)
Total assets	(520,555)	(496,796)
Capitalization:
Common stockholders' equity	(472,187)	(440,014)
Affiliate long-term debt	(36,753)	(44,325)
Total capitalization	(508,940)	(484,339)
Current liabilities:
Payables to affiliates	(11,268)	(12,006)
Accrued expenses and other liabilities	84	32
Total current liabilities	(11,184)	(11,974)
Deferred income taxes, net	(431)	(483)
Total capitalization and liabilities	$ (520,555)	$ (496,796)