Regulated Operating Expenses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Regulated Operating Expenses
Electric transmission and distribution expense	$ 5,530	$ 4,392	$ 16,509	$ 12,764	$ 20,828	$ 16,784
Natural gas transmission and distribution expense	681	554	1,803	1,870	2,376	2,463
Power operation expense (other than fuel)	3,942	4,129	11,953	11,232	15,766	14,898
Customer accounts and assistance expense	3,124	2,621	8,322	7,639	10,894	10,304
Employee pension expense	2,662	2,562	8,062	7,637	10,605	10,118
Employee healthcare expense	2,662	2,442	7,857	7,004	10,678	9,108
General office supplies and expense	2,997	2,530	9,589	7,805	12,560	10,445
Administrative and general expense	3,375	3,675	11,292	11,466	14,917	15,521
Allowance for uncollectible accounts	975	968	2,765	2,313	3,489	3,245
Regulatory reversal of gain on sale of assets			1,236		1,236
Miscellaneous expense	152	165	496	500	675	686
Total	$ 26,100	$ 24,038	$ 79,884	$ 70,230	$ 104,024	$ 93,572