SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 M D	Dec. 31, 2010
Revenue
Maturity period of commercial paper (in days)	90
Minimum percentage over- or under-recovery of the approved revenue requirement to derive pre-determined level (as a percent)	2.50%
Net WRAM and MCBA deferred revenues	$ 12,864
Deferred costs	10,492
Deferred net operating income before income taxes	2,372
Minimum expected collection period for revenues and associated costs reported as net regulatory balancing accounts related to the WRAM and MCBA that are deferred (in months)	24
Expected collection period for operating income reported as net regulatory balancing accounts related to the WRAM and MCBA that are deferred (in months)	24
Unearned revenue liability	1,871	1,569
Regulatory Assets and Liabilities
Net short-term receivable	21,680	14,784
Net long-term receivable	319,898	229,577
Total receivable	319,898	229,577
Net short-term payable	2,655	3,025
Net long-term payable	28,037	17,079
Total payable	28,037	17,079
Net WRAM and MCBA accounts payable
Regulatory Assets and Liabilities
Net short-term payable	543	3,025
Net long-term payable	145	579
Total payable	688	3,604
Net WRAM and MCBA accounts receivable
Regulatory Assets and Liabilities
Net short-term receivable	21,680	14,784
Net long-term receivable	30,268	16,786
Total receivable	$ 49,625	$ 31,570