Regulated Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Regulated Operating Expenses
Electric transmission and distribution expense	$ 7,325	$ 7,463	$ 21,839	$ 21,139	$ 28,619	$ 26,492
Natural gas transmission and distribution expense	592	569	1,997	1,801	2,558	2,496
Power operation expense (other than fuel)	4,258	4,183	13,813	12,195	17,708	15,885
Customer accounts and assistance expense	2,649	2,772	8,142	8,492	10,889	11,350
Employee pension expense	2,769	2,735	8,170	7,963	10,797	10,638
Employee healthcare expense	3,022	2,486	7,640	6,817	9,970	9,150
General office supplies and expense	3,352	3,088	9,032	10,465	13,591	13,725
Administrative and general expense	3,650	3,307	11,647	10,970	15,061	14,479
Allowance for uncollectible accounts	705	915	2,050	3,017	2,453	3,917
Miscellaneous expense	115	255	326	480	448	656
Total	$ 28,437	$ 27,773	$ 84,656	$ 83,339	$ 112,094	$ 108,788