Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
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
AFDUC related to borrowed funds	779,000	$ 0
Capitalized interest on borrowed funds	500,000	700,000
Income tax benefits in excess compensation costs for share-based compensation	500,000
Other changes in noncurrent assets and liabilities	(4,979,000)	(5,070,000)
Net cash provided by operating activities	14,297,000	31,492,000
Repurchase of common stock	(1,119,000)	(466,000)
Net cash provided by financing activities	$ 24,700,000	$ 47,942,000
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
As Reported on Form 10-Q
Summary of Significant Accounting Policies [Line Items]
Other changes in noncurrent assets and liabilities	$ 4,604,000
Net cash provided by operating activities	31,026,000
Repurchase of common stock	0
Net cash provided by financing activities	48,408,000
Increase (Decrease) from Retrospective Adoption
Summary of Significant Accounting Policies [Line Items]
Other changes in noncurrent assets and liabilities	466,000
Net cash provided by operating activities	466,000
Repurchase of common stock	(466,000)
Net cash provided by financing activities	(466,000)
Accounting Standards Update 2016-09
Summary of Significant Accounting Policies [Line Items]
Other changes in noncurrent assets and liabilities	5,070,000
Net cash provided by operating activities	31,492,000
Repurchase of common stock	(466,000)
Net cash provided by financing activities	$ 47,942,000