Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Regulatory Assets and Liabilities
Regulatory assets	$ 379,884	$ 355,930
Regulatory liabilities	44,037	38,735
Short-term portion of the regulatory assets	31,364	30,332
Short-term portion of the regulatory liabilities	4,545	4,759
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities
Regulatory liabilities	33,375	33,231
Health care balancing account
Regulatory Assets and Liabilities
Regulatory liabilities	6,006	0
Conservation program
Regulatory Assets and Liabilities
Regulatory liabilities	2,312	584
Pension balancing account
Regulatory Assets and Liabilities
Regulatory liabilities	383	695
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities
Regulatory liabilities	710	611
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory liabilities	1,251	3,614
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory assets	188,386	188,880
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities
Regulatory assets	94,144	92,099
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory assets	26,540	27,503
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	34,735	16,148
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory assets	16,832	15,812
Interim rates long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	4,616	4,605
Tank coating
Regulatory Assets and Liabilities
Regulatory assets	10,114	8,452
Health care balancing account
Regulatory Assets and Liabilities
Regulatory assets	412	1,000
Pension balancing account
Regulatory Assets and Liabilities
Regulatory assets	1,684	0
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory assets	$ 2,421	$ 1,431