CONDENSED CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2019	$ 215,125	$ 108,667	$ 323,792
Balance, shares at Dec. 31, 2019	17,434
Net Income		30,118	30,118
Dividend Reinvestment & Common Stock Purchase Plan	$ 921		921
Dividend Reinvestment & Common Stock Purchase Plan, shares	14
Restricted Stock Award, Net - Employees	$ 575		575
Restricted Stock Award, Net - Employees, shares	17
Restricted Stock Award - Board of Directors	$ 245		245
Restricted Stock Award - Board of Directors, shares	4
Cash Dividends on Common Stock		(13,418)	(13,418)
Cash Dividends on Preferred Stock		(90)	(90)
Common Stock Issuance Expenses		(37)	(37)
Balance at Sep. 30, 2020	$ 216,866	125,240	342,106
Balance, shares at Sep. 30, 2020	17,469
Balance at Jun. 30, 2020	$ 216,365	117,008	333,373
Balance, shares at Jun. 30, 2020	17,464
Net Income		12,737	12,737
Dividend Reinvestment & Common Stock Purchase Plan	$ 313		313
Dividend Reinvestment & Common Stock Purchase Plan, shares	5
Restricted Stock Award, Net - Employees	$ 188		188
Cash Dividends on Common Stock		(4,475)	(4,475)
Cash Dividends on Preferred Stock		(30)	(30)
Balance at Sep. 30, 2020	$ 216,866	125,240	342,106
Balance, shares at Sep. 30, 2020	17,469
Balance at Dec. 31, 2020	$ 217,451	128,757	346,208
Balance, shares at Dec. 31, 2020	17,473
Net Income		29,305	29,305
Dividend Reinvestment & Common Stock Purchase Plan	$ 885		885
Dividend Reinvestment & Common Stock Purchase Plan, shares	11
Restricted Stock Award, Net - Employees	$ 81		81
Restricted Stock Award, Net - Employees, shares	6
Restricted Stock Award - Board of Directors	$ 245		245
Restricted Stock Award - Board of Directors, shares	3
Cash Dividends on Common Stock		(14,294)	(14,294)
Cash Dividends on Preferred Stock		(90)	(90)
Balance at Sep. 30, 2021	$ 218,662	143,678	362,340
Balance, shares at Sep. 30, 2021	17,493
Balance at Jun. 30, 2021	$ 218,100	136,998	355,098
Balance, shares at Jun. 30, 2021	17,490
Net Income		11,476	11,476
Dividend Reinvestment & Common Stock Purchase Plan	$ 289		289
Dividend Reinvestment & Common Stock Purchase Plan, shares	3
Restricted Stock Award, Net - Employees	$ 273		273
Cash Dividends on Common Stock		(4,766)	(4,766)
Cash Dividends on Preferred Stock		(30)	(30)
Balance at Sep. 30, 2021	$ 218,662	$ 143,678	$ 362,340
Balance, shares at Sep. 30, 2021	17,493