Lines of Credit Narrative (Details) (USD $)						12 Months Ended
	Dec. 31, 2012 Revolving Credit Facility [Member]	Dec. 31, 2012 Revolving Credit Facility [Member] SJW Corp. [Member]	Dec. 31, 2011 Revolving Credit Facility [Member] SJW Corp. [Member]	Mar. 01, 2012 Revolving Credit Facility [Member] Wells Fargo [Member] SJW Corp., SJW Land Company [Member]	Mar. 01, 2012 Revolving Credit Facility [Member] Wells Fargo [Member] San Jose Water Company [Member]	Dec. 31, 2012 Standby Letters of Credit [Member] San Jose Water Company [Member] standy_letter_of_credit
Aggregate amount of unsecured revolving credit facility	$ 90,000,000			$ 15,000,000	$ 75,000,000	$ 3,000,000
Number of standby letters of credit						2
Automatic renewal term of standby letters of credit						1 year
Aggregate outstanding balance on lines of credit		$ 15,300,000	$ 0
Line of Credit Facility, Interest Rate at Period End		1.44%	1.64%