Regulated Operating Expenses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Regulated Operating Expenses
Electric transmission and distribution expense	$ 5,950	$ 4,264	$ 10,979	$ 8,372	$ 19,690	$ 16,493
Natural gas transmission and distribution expense	577	664	1,122	1,316	2,250	2,561
Power operation expense (other than fuel)	4,515	3,604	8,307	7,399	16,545	15,529
Customer accounts and assistance expense	2,619	2,584	5,198	5,018	10,391	10,297
Employee pension expense	2,757	2,539	5,399	5,074	10,505	10,060
Employee healthcare plan	2,408	2,324	5,195	4,562	10,458	8,664
General office supplies and expense	3,163	2,523	6,592	5,275	12,093	10,298
Administrative and general expense	3,603	3,573	7,918	7,792	15,217	15,384
Allowance for uncollectible accounts	1,044	753	1,790	1,345	3,483	3,446
Regulatory reversal of gain on sale of assets			1,236		1,236
Miscellaneous expense	11	16	48	39	95	102
Total	$ 26,647	$ 22,844	$ 53,784	$ 46,192	$ 101,963	$ 92,834