Statements of Cash Flows (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM INVESTING ACTIVITIES:
Utility plant additions, debt portion of allowance for funds used during construction	$ 59	$ 55	$ 62
Supplemental schedule of non-cash investing and financing activities:
Accounts payable, construction of utility plant	674	600	726
Short-term line of credit borrowings, reclassified as long-term borrowings			$ 3,000