Condensed Consolidating Financial Statements (Details 2) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Dec. 31, 2013
Utility plant:        
Utility plant $ 2,373,167 $ 2,342,471    
Less accumulated depreciation and amortization (766,545) (752,040)    
Net utility plant 1,606,622 1,590,431    
Current assets:        
Cash and cash equivalents 33,311 19,587 21,744 27,506
Receivables and unbilled revenue 110,291      
Receivables   116,878    
Other current assets 15,653 17,659    
Total current assets 159,255 154,124    
Other assets:        
Regulatory assets 401,089 390,331    
Other assets 53,779 52,465    
Total other assets 454,868 442,796    
Total assets 2,220,745 2,187,351    
Capitalization:        
Common stockholders' equity 620,666 626,626    
Long-term debt, less current maturities 419,014 419,233    
Total capitalization 1,039,680 1,045,859    
Current liabilities:        
Current maturities of long-term debt 6,596 6,607    
Short-term borrowings 109,115 79,115    
Accounts payable 57,684 59,395    
Accrued expenses and other liabilities 80,548 72,589    
Total current liabilities 253,943 217,706    
Unamortized investment tax credits 2,032 2,032    
Deferred income taxes, net 214,814 214,842    
Pension and postretirement benefits other than pensions 277,094 270,865    
Regulatory and other liabilities 81,499 83,279    
Advances for construction 181,553 182,284    
Contributions in aid of construction 170,130 170,484    
Total capitalization and liabilities 2,220,745 2,187,351    
Consolidating Adjustments        
Utility plant:        
Utility plant (7,197) (7,197)    
Less accumulated depreciation and amortization 1,747 1,722    
Net utility plant (5,450) (5,475)    
Current assets:        
Receivables   (1,051)    
Receivables from affiliates (24,202) (23,609)    
Total current assets (24,202) (24,660)    
Other assets:        
Investments in affiliates (632,396) (637,998)    
Long-term affiliate notes receivable (25,006) (25,263)    
Other assets (1,124) (321)    
Total other assets (658,526) (663,582)    
Total assets (688,178) (693,717)    
Capitalization:        
Common stockholders' equity (637,808) (643,426)    
Affiliate long-term debt (25,006) (25,263)    
Total capitalization (662,814) (668,689)    
Current liabilities:        
Payables to affiliates (24,202) (23,609)    
Accounts payable   (201)    
Accrued expenses and other liabilities 9 (756)    
Total current liabilities (24,193) (24,566)    
Deferred income taxes, net (1,171) (462)    
Total capitalization and liabilities (688,178) (693,717)    
Parent Company        
Utility plant:        
Utility plant 1,318 1,318    
Less accumulated depreciation and amortization (434) (377)    
Net utility plant 884 941    
Current assets:        
Cash and cash equivalents 316 4,108 512 5,280
Receivables from affiliates 23,235 20,001    
Other current assets 406      
Total current assets 23,957 24,109    
Other assets:        
Investments in affiliates 632,396 637,998    
Long-term affiliate notes receivable 25,006 25,263    
Other assets 894 891    
Total other assets 658,296 664,152    
Total assets 683,137 689,202    
Capitalization:        
Common stockholders' equity 620,666 626,626    
Total capitalization 620,666 626,626    
Current liabilities:        
Short-term borrowings 61,715 61,715    
Accrued expenses and other liabilities 116 861    
Total current liabilities 61,831 62,576    
Deferred income taxes, net 640      
Total capitalization and liabilities 683,137 689,202    
Cal Water        
Utility plant:        
Utility plant 2,183,726 2,154,146    
Less accumulated depreciation and amortization (723,893) (710,840)    
Net utility plant 1,459,833 1,443,306    
Current assets:        
Cash and cash equivalents 31,200 13,929 20,097 20,790
Receivables and unbilled revenue 106,800      
Receivables   108,815    
Receivables from affiliates 883 3,608    
Other current assets 14,016 16,443    
Total current assets 152,899 142,795    
Other assets:        
Regulatory assets 398,090 387,387    
Other assets 48,829 47,617    
Total other assets 446,919 435,004    
Total assets 2,059,651 2,021,105    
Capitalization:        
Common stockholders' equity 563,439 569,319    
Long-term debt, less current maturities 417,678 417,884    
Total capitalization 981,117 987,203    
Current liabilities:        
Current maturities of long-term debt 6,182 6,173    
Short-term borrowings 47,400 17,400    
Payables to affiliates 1,579 270    
Accounts payable 54,851 56,666    
Accrued expenses and other liabilities 78,199 71,203    
Total current liabilities 188,211 151,712    
Unamortized investment tax credits 2,032 2,032    
Deferred income taxes, net 215,345 210,789    
Pension and postretirement benefits other than pensions 277,094 270,865    
Regulatory and other liabilities 72,456 74,282    
Advances for construction 181,039 181,763    
Contributions in aid of construction 142,357 142,459    
Total capitalization and liabilities 2,059,651 2,021,105    
All Other Subsidiaries        
Utility plant:        
Utility plant 195,320 194,204    
Less accumulated depreciation and amortization (43,965) (42,545)    
Net utility plant 151,355 151,659    
Current assets:        
Cash and cash equivalents 1,795 1,550 1,135 1,436
Receivables and unbilled revenue 3,491      
Receivables   9,114    
Receivables from affiliates 84      
Other current assets 1,231 1,216    
Total current assets 6,601 11,880    
Other assets:        
Regulatory assets 2,999 2,944    
Other assets 5,180 4,278    
Total other assets 8,179 7,222    
Total assets 166,135 170,761    
Capitalization:        
Common stockholders' equity 74,369 74,107    
Affiliate long-term debt 25,006 25,263    
Long-term debt, less current maturities 1,336 1,349    
Total capitalization 100,711 100,719    
Current liabilities:        
Current maturities of long-term debt 414 434    
Payables to affiliates 22,623 23,339    
Accounts payable 2,833 2,930    
Accrued expenses and other liabilities 2,224 1,281    
Total current liabilities 28,094 27,984    
Deferred income taxes, net   4,515    
Regulatory and other liabilities 9,043 8,997    
Advances for construction 514 521    
Contributions in aid of construction 27,773 28,025    
Total capitalization and liabilities $ 166,135 $ 170,761