Statements of Common Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2014	$ 77,556	$ 27,007	$ 104,563
Balance (in shares) at Dec. 31, 2014	12,830,521
Net income	$ 0	5,453	5,453
Dividends	0	(3,843)	$ (3,843)
Retirement of common stock (in shares)			0
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 1,157	0	$ 1,157
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	51,573
Balance at Jun. 30, 2015	$ 78,713	28,617	107,330
Balance (in shares) at Jun. 30, 2015	12,882,094
Balance at Dec. 31, 2015	$ 77,317	31,753	$ 109,070
Balance (in shares) at Dec. 31, 2015	12,812,377		12,812,377
Net income	$ 0	5,333	$ 5,333
Dividends	0	(3,994)	$ (3,994)
Retirement of common stock (in shares)			0
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 1,568	0	$ 1,568
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	55,359
Balance at Jun. 30, 2016	$ 78,885	$ 33,092	$ 111,977
Balance (in shares) at Jun. 30, 2016	12,867,736		12,867,736