Segment and Nonregulated Business Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 reportable_segment subsidiaries		Dec. 31, 2012		Dec. 31, 2011
Segment Reporting Information [Line Items]
Number of Subsidiaries											4
Operating revenue	$ 67,262		$ 85,238	$ 74,230	$ 50,139	$ 62,449		$ 82,374	$ 65,575	$ 51,149	$ 276,869		$ 261,547		$ 238,955
Utilities Operating Expense											223,462		206,250		184,564
Operating Income (Loss)	11,351		19,346	16,937	5,773	14,110		20,877	13,585	6,725	53,407		55,297		54,391
Net income	4,677		8,950	7,440	1,317	5,924		10,084	5,201	1,109	22,384		22,318		20,878
Depreciation and amortization											35,039		33,098		31,193
Provision for income taxes											14,135		15,542		14,566
Assets	1,109,986					1,087,499					1,109,986		1,087,499
Number of Reportable Segments											2
SJW Corp. [Member]
Segment Reporting Information [Line Items]
Operating revenue											276,869		261,547		238,955
Utilities Operating Expense											223,462		206,250		184,564
Operating Income (Loss)											53,407		55,297		54,391
Net income											22,384		22,318		20,878
Depreciation and amortization											35,039		33,098		31,193
Interest Expense											19,922		20,185		19,675
Provision for income taxes											14,135		15,542		14,566
Assets	1,109,986					1,087,499					1,109,986		1,087,499		1,038,810
Regulated [Member] | Water Utility Services [Member]
Segment Reporting Information [Line Items]
Operating revenue											264,782		251,032		229,411
Utilities Operating Expense											212,761		197,893		175,812
Operating Income (Loss)											52,021		53,139		53,599
Net income											23,273		22,811		21,970
Depreciation and amortization											33,067		31,085		29,136
Interest Expense											16,616		16,499		16,741
Provision for income taxes											14,446		15,678		15,387
Assets	1,013,229					991,866					1,013,229		991,866		917,580
Regulated [Member] | SJW Corp. [Member]
Segment Reporting Information [Line Items]
Operating revenue											264,782		251,032		229,411
Utilities Operating Expense											212,761		197,893		175,812
Operating Income (Loss)											52,021		53,139		53,599
Net income											23,273		22,811		21,970
Depreciation and amortization											33,067		31,085		29,136
Interest Expense											16,616		16,499		16,741
Provision for income taxes											14,446		15,678		15,387
Assets	1,013,229					991,866					1,013,229		991,866		917,580
Nonregulated [Member] | Water Utility Services [Member]
Segment Reporting Information [Line Items]
Operating revenue											5,882		5,523		4,935
Utilities Operating Expense											5,683		4,043		3,481
Operating Income (Loss)											199		1,480		1,454
Net income											(208)		707		765
Depreciation and amortization											360		360		360
Interest Expense											0		0		0
Provision for income taxes											124		581		571
Assets	16,163					13,245					16,163		13,245		11,668
Nonregulated [Member] | Real Estate Services [Member]
Segment Reporting Information [Line Items]
Operating revenue											6,205		4,992		4,609
Utilities Operating Expense											4,000		3,379		3,240
Operating Income (Loss)											2,205		1,613		1,369
Net income											920		244		(407)
Depreciation and amortization											1,612		1,653		1,697
Interest Expense											1,120		1,511		1,833
Provision for income taxes											768		374		(296)
Assets	71,779					74,903					71,779		74,903		80,097
Nonregulated [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Operating revenue											0	[1]	0	[1]	0	[1]
Utilities Operating Expense											1,018	[1]	935	[1]	2,031	[1]
Operating Income (Loss)											(1,018)	[1]	(935)	[1]	(2,031)	[1]
Net income											(1,601)	[1]	(1,444)	[1]	(1,450)	[1]
Depreciation and amortization											0	[1]	0	[1]	0	[1]
Interest Expense											2,186	[1]	2,175	[1]	1,101	[1]
Provision for income taxes											(1,203)	[1]	(1,091)	[1]	(1,096)	[1]
Assets	8,815	[1]				7,485	[1]				8,815	[1]	7,485	[1]	29,465	[1]
Nonregulated [Member] | SJW Corp. [Member]
Segment Reporting Information [Line Items]
Operating revenue											12,087		10,515		9,544
Utilities Operating Expense											10,701		8,357		8,752
Operating Income (Loss)											1,386		2,158		792
Net income											(889)		(493)		(1,092)
Depreciation and amortization											1,972		2,013		2,057
Interest Expense											3,306		3,686		2,934
Provision for income taxes											(311)		(136)		(821)
Assets	$ 96,757					$ 95,633					$ 96,757		$ 95,633		$ 121,230

[1] The “All Other” category includes the accounts of SJW Corp. on a stand-alone basis.