Statements of Common Stockholders' Equity (Unaudited) (USD $) In Thousands, except Share data	Common Stock [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2011	$ 77,113	$ 18,152	$ 95,265
Balance (in shares) at Dec. 31, 2011	12,791,671
Net income	0	1,941	1,941
Dividends	0	(1,710)	(1,710)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	568	0	568
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	32,718
Balance at Mar. 31, 2012	77,681	18,383	96,064
Balance (in shares) at Mar. 31, 2012	12,824,389
Balance at Dec. 31, 2012	79,299	20,526	99,825
Balance (in shares) at Dec. 31, 2012	12,918,633		12,918,633
Net income	0	2,139	2,139
Dividends	0	(1,790)	(1,790)
Retirement of common stock	(197)	0	(197)
Retirement of common stock (in shares)	(10,639)		(10,639)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	776	0	776
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	42,761
Balance at Mar. 31, 2013	$ 79,878	$ 20,875	$ 100,753
Balance (in shares) at Mar. 31, 2013	12,950,755		12,950,755