Statements of Common Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2015	$ 77,317	$ 31,753	$ 0	$ 109,070
Balance (in shares) at Dec. 31, 2015	12,812,377
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	2,486	0	2,486
Dividends	0	(1,995)	0	$ (1,995)
Repurchase of common stock (in shares)				0
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 733	0	0	$ 733
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	27,358
Balance at Mar. 31, 2016	$ 78,050	32,244	0	110,294
Balance (in shares) at Mar. 31, 2016	12,839,735
Balance at Dec. 31, 2016	$ 78,513	35,548	0	$ 114,061
Balance (in shares) at Dec. 31, 2016	12,852,295			12,852,295
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	2,581	0	$ 2,581
Dividends	0	(2,060)	0	(2,060)
Repurchase of common stock	$ 0	0	(825)	$ (825)
Repurchase of common stock (in shares)	(24,329)			(24,329)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 522	0	0	$ 522
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	15,084
Stock-based compensation	$ 2	0	0	2
Stock-based compensation (in shares)	0
Balance at Mar. 31, 2017	$ 79,037	$ 36,069	$ (825)	$ 114,281
Balance (in shares) at Mar. 31, 2017	12,843,050			12,843,050