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	4,145	4,145
Dividends	0	(3,425)	(3,425)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	1,092	0	1,092
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	63,800
Balance at Jun. 30, 2012	78,205	18,872	97,077
Balance (in shares) at Jun. 30, 2012	12,855,471
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	4,481	4,481
Dividends	0	(3,572)	(3,572)
Retirement of common stock	(1,746)	0	(1,746)
Retirement of common stock (in shares)	(93,052)		(93,052)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	1,344	0	1,344
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	73,517
Balance at Jun. 30, 2013	$ 78,897	$ 21,435	$ 100,332
Balance (in shares) at Jun. 30, 2013	12,899,098		12,899,098