Long-Term Liabilities and Bank Borrowings (Details) - USD ($)		6 Months Ended
	Jun. 29, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 01, 2016	May 31, 2016	Dec. 31, 2015	Mar. 01, 2012
Debt Instrument [Line Items]
Long-term Debt		$ 4,885,000	$ 314,000
San Jose Water Company [Member] | Chase Bank, N.A. [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 10,000,000
San Jose Water Company [Member] | Chase Bank, N.A. [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				125,000,000
San Jose Water Company [Member] | Wells Fargo Bank, National Association [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				3,000,000
San Jose Water Company [Member] | Wells Fargo Bank, National Association [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				3,060,000	$ 85,000,000
San Jose Water Company [Member] | SDWSRF Loans [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 1,823,000
San Jose Water Company [Member] | Chase Bank and Wells Fargo Bank [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		125,000,000
SJW Corp. and SJW Land Company [Member] | Chase Bank, N.A. [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				5,000,000
SJW Corp. and SJW Land Company [Member] | Chase Bank, N.A. [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				15,000,000
SJW Corp. and SJW Land Company [Member] | Wells Fargo Bank, National Association [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity							$ 15,000,000
SJW Corp. and SJWTX, Inc. [Member] | Chase Bank, N.A. [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				1,000,000
SJW Corp. and SJWTX, Inc. [Member] | Chase Bank, N.A. [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 5,000,000
Adjustments for New Accounting Pronouncement [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense		$ 3,561,000				$ 3,638,000