Statements of Common Stockholders' Equity (Unaudited) (USD $) In Thousands, except Share data	Common Stock [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2012	$ 79,299	$ 20,526	$ 99,825
Balance (in shares) at Dec. 31, 2012	12,918,633
Net income	0	7,016	7,016
Dividends	0	(5,359)	(5,359)
Retirement of common stock	(1,772)	0	(1,772)
Retirement of common stock (in shares)	(94,414)		(94,414)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	2,075	0	2,075
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	109,476
Balance at Sep. 30, 2013	79,602	22,183	101,785
Balance (in shares) at Sep. 30, 2013	12,933,695
Balance at Dec. 31, 2013	80,545	22,966	103,511
Balance (in shares) at Dec. 31, 2013	12,979,281		12,979,281
Net income	0	7,933	7,933
Dividends	0	(5,527)	(5,527)
Retirement of common stock	(5,180)	0	(5,180)
Retirement of common stock (in shares)	(256,943)		(256,943)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	2,144	0	2,144
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	108,376
Balance at Sep. 30, 2014	$ 77,509	$ 25,372	$ 102,881
Balance (in shares) at Sep. 30, 2014	12,830,714		12,830,714