Statements of Common Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2013	$ 80,545	$ 22,966	$ 103,511
Balance (in shares) at Dec. 31, 2013	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
Balance at Dec. 31, 2014	$ 77,556	27,007	$ 104,563
Balance (in shares) at Dec. 31, 2014	12,830,521		12,830,521
Net income	$ 0	8,973	$ 8,973
Dividends	0	(5,753)	(5,753)
Retirement of common stock	$ (2,495)	0	$ (2,495)
Retirement of common stock (in shares)	(118,812)		(118,812)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 1,762	0	$ 1,762
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	80,349
Balance at Sep. 30, 2015	$ 76,823	$ 30,227	$ 107,050
Balance (in shares) at Sep. 30, 2015	12,792,058		12,792,058