Statements of Common Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2017	$ 79,201	$ 40,204	$ 119,405
Balance (in shares) at Dec. 31, 2017	12,872,742
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	2,594	2,594
Dividends	0	(2,146)	(2,146)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 591	0	591
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	20,056
Stock-based compensation	$ 4	0	4
Stock-based compensation (in shares)	0
Balance at Mar. 31, 2018	$ 79,796	40,652	120,448
Balance (in shares) at Mar. 31, 2018	12,892,798
Balance at Dec. 31, 2018	$ 81,305	44,890	$ 126,195
Balance (in shares) at Dec. 31, 2018	12,943,536		12,943,536
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	2,813	$ 2,813
Dividends	0	(2,243)	(2,243)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 384	0	384
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	11,440
Stock-based compensation	$ 14	0	14
Stock-based compensation (in shares)	0
Balance at Mar. 31, 2019	$ 81,703	$ 45,460	$ 127,163
Balance (in shares) at Mar. 31, 2019	12,954,976		12,954,976