Summary of Significant Accounting Policies (Details) (USD $)	6 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Summary of Significant Accounting Policies
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%
Current assets included in the net regulatory balancing accounts	$ 13,085,000	$ 14,784,000
Current liabilities included in the net regulatory balancing accounts	2,297,000	3,025,000
Long-term assets included in the net regulatory balancing accounts	28,100,000	16,800,000
Long-term liabilities included in the net regulatory balancing accounts	$ 500,000	$ 600,000

- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References+ Details