Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Summary of Significant Accounting Policies [Line Items]
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	$ 800,000		$ 800,000		$ 800,000
Allowance for equity funds used during construction	879,000	$ 0	1,658,000	$ 0
Allowance for borrowed funds used during construction	564,000	837,000	1,058,000	1,567,000
Allowance for Equity and Borrowed Funds Used During Construction	1,443,000	837,000	2,716,000	1,567,000
Allowance for equity funds used during construction, Change	879,000		1,658,000
Allowance for borrowed funds used during construction, Change	(273,000)		(509,000)
Allowance for Equity and Borrowed Funds Used During Construction, Change	606,000		1,149,000
Carrying value of cash and cash equivalents	29,103,000	$ 30,826,000	29,103,000	30,826,000	25,492,000	$ 8,837,000
Income tax benefits in excess compensation costs for share-based compensation				500,000
Other changes in noncurrent assets and liabilities			19,687,000	16,757,000
Net cash provided by operating activities			35,726,000	59,611,000
Repurchase of common stock			(1,236,000)	(548,000)
Net cash provided by financing activities			77,961,000	79,756,000
As Reported on Form 10-Q
Summary of Significant Accounting Policies [Line Items]
Other changes in noncurrent assets and liabilities				16,209,000
Net cash provided by operating activities				59,063,000
Repurchase of common stock				0
Net cash provided by financing activities				80,304,000
Taxes, prepaid expenses and other assets
Summary of Significant Accounting Policies [Line Items]
Carrying value of restricted cash	$ 1,000,000		$ 1,000,000		$ 400,000
Minimum
Summary of Significant Accounting Policies [Line Items]
Expected collection period for undercollected net WRAM and MCBA receivables			12 months
Maximum
Summary of Significant Accounting Policies [Line Items]
Expected collection period for undercollected net WRAM and MCBA receivables			18 months
Accounting Standards Update 2016-09 | Increase (Decrease) from Retrospective Adoption
Summary of Significant Accounting Policies [Line Items]
Other changes in noncurrent assets and liabilities				548,000
Net cash provided by operating activities				548,000
Repurchase of common stock				(548,000)
Net cash provided by financing activities				$ (548,000)