Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Regulatory Assets and Liabilities
Regulatory assets	$ 375,868	$ 355,930
Regulatory liabilities	40,569	38,735
Short-term portion of the regulatory assets	29,071	30,332
Short-term portion of the regulatory liabilities	6,743	4,759
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities
Regulatory liabilities	33,317	33,231
Health care balancing account
Regulatory Assets and Liabilities
Regulatory liabilities	4,224	0
Conservation program
Regulatory Assets and Liabilities
Regulatory liabilities	1,358	584
Pension balancing account
Regulatory Assets and Liabilities
Regulatory liabilities	146	695
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities
Regulatory liabilities	720	611
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory liabilities	804	3,614
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory assets	188,550	188,880
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities
Regulatory assets	93,326	92,099
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory assets	26,663	27,503
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	33,327	16,148
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory assets	16,488	15,812
Interim rates long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	4,634	4,605
Tank coating
Regulatory Assets and Liabilities
Regulatory assets	9,501	8,452
Health care balancing account
Regulatory Assets and Liabilities
Regulatory assets	227	1,000
Pension balancing account
Regulatory Assets and Liabilities
Regulatory assets	910	0
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory assets	$ 2,242	$ 1,431