Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Regulatory Assets and Liabilities
Regulatory assets	$ 398,535	$ 390,331
Regulatory liabilities	36,127	36,447
Short-term portion of the regulatory assets	38,112	53,199
Short-term portion of the regulatory liabilities	1,870	6,126
Tax benefits to ratepayers
Regulatory Assets and Liabilities
Regulatory liabilities	26,620	26,114
Conservation program
Regulatory Assets and Liabilities
Regulatory liabilities	4,686	2,669
Pension balancing account
Regulatory Assets and Liabilities
Regulatory liabilities	2,181	4,291
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory liabilities	2,640	3,373
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory assets	244,514	245,008
Tax benefits to ratepayers
Regulatory Assets and Liabilities
Regulatory assets	73,797	72,350
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory assets	29,356	32,959
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	16,972	14,449
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory assets	14,792	13,863
Interim rates long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	5,694	10,627
Tank coating
Regulatory Assets and Liabilities
Regulatory assets	7,264	0
Health care balancing account
Regulatory Assets and Liabilities
Regulatory assets	4,445	1,075
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory assets	$ 1,701	$ 0