Statements of Common Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2018	$ 81,305	$ 44,890	$ 126,195
Balance (in shares) at Dec. 31, 2018	12,943,536
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	2,813	2,813
Cash dividends declared	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
Balance at Dec. 31, 2019	$ 83,976	50,209	$ 134,185
Balance (in shares) at Dec. 31, 2019	13,014,898		13,014,898
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	4,002	$ 4,002
Cash dividends declared	0	(2,346)	(2,346)
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans	$ 411	0	411
Issuance of common stock under dividend reinvestment, direct stock and employee stock purchase plans (in shares)	9,289
Stock-based compensation	$ 37	0	37
Stock-based compensation (in shares)	0
Balance at Mar. 31, 2020	$ 84,424	$ 51,865	$ 136,289
Balance (in shares) at Mar. 31, 2020	13,024,187		13,024,187