Regulated Operating Expenses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Regulated Operating Expenses
Electric transmission and distribution expense	$ 4,392	$ 4,101	$ 12,764	$ 11,341	$ 16,784	$ 14,918
Natural gas transmission and distribution expense	554	652	1,870	1,793	2,463	2,399
Power operation expense (other than fuel)	4,277	4,316	11,676	9,463	15,490	11,984
Customer accounts and assistance expense	2,621	2,614	7,639	7,545	10,304	10,353
Employee pension expense	2,562	2,504	7,637	6,323	10,118	8,116
Employee healthcare expense	2,442	1,999	7,004	5,336	9,108	7,082
General office supplies and expense	2,530	2,382	7,805	7,517	10,445	10,942
Administrative and general expense	3,675	3,537	11,466	10,240	15,521	13,504
Allowance for uncollectible accounts	968	1,169	2,313	2,494	3,245	3,511
Miscellaneous expense	17	25	56	48	94	86
Total	$ 24,038	$ 23,299	$ 70,230	$ 62,100	$ 93,572	$ 82,895