Long-Term Debt Narrative (Details) (USD $)			12 Months Ended				12 Months Ended
	Dec. 31, 2012 Significant Observable Inputs (Level 2)	Dec. 31, 2011 Significant Observable Inputs (Level 2)	Dec. 31, 2012 San Jose Water Company [Member] Senior Notes [Member]	Dec. 31, 2012 SJWTX,Inc. dba Canyon Lake Water Supply Corporation [Member] Senior Notes [Member] Series A [Member]	Dec. 31, 2012 SJW Corp. [Member] Senior Notes [Member] Series A [Member]	Dec. 31, 2012 SJW Corp. [Member] Senior Notes [Member] Series A [Member] Financial Guarantee [Member]	Dec. 31, 2012 SJW Corp. [Member] Senior Notes [Member] Series A [Member] Financial Guarantee [Member] Minimum [Member]
Ratio of indebtedness to total capital			0.6666	0.6666	0.6666	0.6666
Ratio of net income available for interest charges for the trailing 12-month calendar period to interest charges			1.75	1.75
Minimum net worth required for compliance					$ 175,000,000		$ 125,000,000
Cumulative net income, percentage included in net worth for compliance					30.00%		30.00%
Fair value of long-term debt	$ 455,042,000	$ 433,873,000