Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Regulatory Assets and Liabilities
Regulatory assets	$ 361,249	$ 361,893
Regulatory liabilities	40,765	35,264
Short-term portion of the regulatory assets	31,554	35,052
Short-term portion of the regulatory liabilities	1,075	2,227
Tax benefits to ratepayers
Regulatory Assets and Liabilities
Regulatory liabilities	29,505	29,505
Conservation program
Regulatory Assets and Liabilities
Regulatory liabilities	2,454	2,317
Pension balancing account
Regulatory Assets and Liabilities
Regulatory liabilities	1,646	792
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory liabilities	7,160	2,650
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory assets	205,449	205,614
Tax benefits to ratepayers
Regulatory Assets and Liabilities
Regulatory assets	81,522	81,522
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory assets	28,314	27,327
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	12,873	15,410
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory assets	15,003	14,682
Interim rates long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	4,852	5,238
Tank coating
Regulatory Assets and Liabilities
Regulatory assets	7,341	6,829
Health care balancing account
Regulatory Assets and Liabilities
Regulatory assets	3,948	3,503
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory assets	$ 1,947	$ 1,768