Balancing and Memorandum Account Recovery Procedures (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Jan. 03, 2012	Dec. 31, 2011
Balancing and Memorandum Account Recovery Procedures [Abstract]
Balancing Account, Net	$ 3,054		$ 3,686
Recovery amount requested in the general rate case		2,599
Memorandum Account, Net	(169)		255
Amount of net over-collection requested to be refunded to customers		$ 653
Threshold as a percentage of authorized revenue for balancing account or memorandum account review	2.00%

This represents the under-collection or over-collection associated with expense changes and the revenue authorized by the CPUC to offset those expense changes. Pursuant to Section 792.5 of the California Public Utilities Code, a balancing account must be maintained for expense items for which revenue offsets have been authorized. Since the amounts in the balancing accounts must be approved by the CPUC before they can be incorporated into rates, the Company does not recognize balancing accounts in its revenue until CPUC approval occurs. It is typical for the CPUC to incorporate any over-collected and/or under-collected balances in balancing accounts into customer rates at the time rate decisions are made as part of the Company’s general rate case proceedings by assessing temporary surcredits and/or surcharges.

No definition available.

Name:	sjw_BalancingAccountNet
Namespace Prefix:	sjw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant