Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Revenue
Markup for return or profit for cost-recovery expenses	$ 0
Maturity period of commercial paper	90 days
Minimum collection period after net receivable balances were recognized in which the Company defers net WRAM and MCBA operating revenues and associated costs	24 months
Maximum collection period in which deferred net WRAM and MCBA revenues and associated costs will be recognized	24 months
Unearned revenue liability	$ (1,100,000)	$ (1,300,000)
Regulatory Assets and Liabilities
Expected collection period for undercollected net WRAM and MCBA receivables		18 months
Cash and Cash Equivalents
Carrying value of cash and cash equivalents	30,878,000	$ 8,837,000	$ 33,311,000	$ 19,587,000
Taxes, prepaid expenses and other assets [Member]
Regulatory Assets and Liabilities
Carrying value of restricted cash	$ 1,000,000	$ 500,000
Minimum
Regulatory Assets and Liabilities
Expected collection period for undercollected net WRAM and MCBA receivables		12 months
Maximum
Regulatory Assets and Liabilities
Expected collection period for undercollected net WRAM and MCBA receivables		20 months