Regulated Operating Expenses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Regulated Operating Expenses
Electric transmission and distribution expense	$ 4,264	$ 3,418	$ 8,372	$ 7,240	$ 16,493	$ 14,265
Natural gas transmission and distribution expense	664	579	1,316	1,141	2,561	2,289
Power operation expense (other than fuel)	3,604	2,469	7,399	5,147	15,529	10,807
Customer accounts and assistance expense	2,584	2,395	5,018	4,931	10,297	10,632
Employee pension expense	2,539	1,975	5,074	3,819	10,060	6,967
Employee healthcare plan	2,324	1,716	4,562	3,337	8,664	7,022
General office supplies and expense	2,523	2,236	5,275	5,135	10,298	11,338
Administrative and general expense	3,573	3,057	7,792	6,704	15,384	12,966
Allowance for uncollectible accounts	753	1,242	1,345	1,324	3,446	3,520
Miscellaneous expense	16	(2)	39	23	102	98
Total	$ 22,844	$ 19,085	$ 46,192	$ 38,801	$ 92,834	$ 79,904