CONSOLIDATED STATEMENTS OF CAPITAL STOCK AND LONG-TERM DEBT - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Common Stock, No Par Value	$ 217,451	$ 215,125
Retained Earnings	128,757	108,667
TOTAL COMMON EQUITY	346,208	323,792
TOTAL PREFERRED STOCK	2,084	2,084
SUBTOTAL LONG-TERM DEBT	277,241	234,397
Add: Premium on Issuance of Long-term Debt	7,669	8,064
Less: Unamortized Debt Expense	(4,411)	(4,506)
Less: Current Portion of Long-term Debt	(7,255)	(7,178)
TOTAL LONG-TERM DEBT	273,244	230,777
Convertible Preferred Stock $7.00 Series
SUBTOTAL LONG-TERM DEBT	1,005	1,005
Nonredeemable Preferred Stock $7.00 Series
SUBTOTAL LONG-TERM DEBT	79	79
Nonredeemable Preferred Stock $4.75 Series [Member]
SUBTOTAL LONG-TERM DEBT	1,000	1,000
Amortizing Secured Note, due December 20, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	336	643
Amortizing Secured Note, due May 19, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	3,115	3,535
Amortizing Secured Note, due August 25, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	2,707	2,987
Amortizing Secured Note, due September 19, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	2,987	3,267
State Revolving Trust Note, due December 31, 2022 [Member]
SUBTOTAL LONG-TERM DEBT	119	175
State Revolving Trust Note, due May 1, 2025 [Member]
SUBTOTAL LONG-TERM DEBT	1,170	1,405
State Revolving Trust Note, due March 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	266	309
State Revolving Trust Note, due January 25, 2027 [Member]
SUBTOTAL LONG-TERM DEBT	307	349
State Revolving Trust Note, due December 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	389	446
State Revolving Trust Bond 4.00% to 5.00%, due August 1, 2021 [Member]
SUBTOTAL LONG-TERM DEBT		60
State Revolving Trust Bond 0.00%, due August 1, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	11	50
State Revolving Trust Note, due July 1, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	192	214
State Revolving Trust Note, due January 1, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	62	69
State Revolving Trust Note, due August 1, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	793	851
Amortizing Secured Note, due April 20, 2029 [Member]
SUBTOTAL LONG-TERM DEBT	2,907	3,255
Amortizing Secured Note 7.05%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	2,271	2,521
Amortizing Secured Note 5.69%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	4,658	5,171
4.45%, Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	8,506	8,946
4.47%, Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	3,156	3,320
State Revolving Trust Note, due July 1, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	1,699	1,829
State Revolving Trust Note, due February 1, 2036 [Member]
SUBTOTAL LONG-TERM DEBT	961	1,013
State Revolving Trust Note, due February 1, 2038 [Member]
SUBTOTAL LONG-TERM DEBT	1,543	1,309
State Revolving Trust Note, due November 30, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	883	955
Construction Loans [Member]
SUBTOTAL LONG-TERM DEBT	50,536	40,467
First Mortgage Bonds - Series BB [Member]
SUBTOTAL LONG-TERM DEBT	119	241
First Mortgage Bonds - Series CC [Member]
SUBTOTAL LONG-TERM DEBT	164	331
First Mortgage Bonds - Series EE [Member]
SUBTOTAL LONG-TERM DEBT	1,036	1,456
First Mortgage Bonds - Series FF [Member]
SUBTOTAL LONG-TERM DEBT	1,870	2,440
First Mortgage Bonds - Series GG [Member]
SUBTOTAL LONG-TERM DEBT	541	632
First Mortgage Bonds - Series HH [Member]
SUBTOTAL LONG-TERM DEBT	620	710
First Mortgage Bonds - Series II [Member]
SUBTOTAL LONG-TERM DEBT	338	429
First Mortgage Bonds - Series JJ [Member]
SUBTOTAL LONG-TERM DEBT	500	588
First Mortgage Bonds - Series KK [Member]
SUBTOTAL LONG-TERM DEBT	719	807
First Mortgage Bonds - Series LL [Member]
SUBTOTAL LONG-TERM DEBT	846	928
First Mortgage Bonds - Series MM [Member]
SUBTOTAL LONG-TERM DEBT	937	1,037
First Mortgage Bonds - Series NN [Member]
SUBTOTAL LONG-TERM DEBT	1,105	1,190
First Mortgage Bonds - Series OO [Member]
SUBTOTAL LONG-TERM DEBT	1,656	1,806
First Mortgage Bonds - Series PP [Member]
SUBTOTAL LONG-TERM DEBT	600	660
First Mortgage Bonds - Series QQ [Member]
SUBTOTAL LONG-TERM DEBT	9,915	9,915
First Mortgage Bonds - Series RR [Member]
SUBTOTAL LONG-TERM DEBT	22,500	22,500
First Mortgage Bonds - Series SS [Member]
SUBTOTAL LONG-TERM DEBT	23,000	23,000
First Mortgage Bonds - Series TT [Member]
SUBTOTAL LONG-TERM DEBT	1,806	1,957
First Mortgage Bonds - Series UU [Member]
SUBTOTAL LONG-TERM DEBT	705	755
First Mortgage Bonds - Series VV [Member]
SUBTOTAL LONG-TERM DEBT	1,861	2,004
First Mortgage Bonds - Series WW [Member]
SUBTOTAL LONG-TERM DEBT	715	755
First Mortgage Bonds - Series XX [Member]
SUBTOTAL LONG-TERM DEBT	10,247	10,627
First Mortgage Bonds - Series YY [Member]
SUBTOTAL LONG-TERM DEBT	3,710	3,785
First Mortgage Bonds - Series 2018A [Member]
SUBTOTAL LONG-TERM DEBT	6,246	6,678
First Mortgage Bonds - Series 2018B [Member]
SUBTOTAL LONG-TERM DEBT	2,211	2,320
First Mortgage Bonds - Series 2019A [Member]
SUBTOTAL LONG-TERM DEBT	32,500	32,500
First Mortgage Bonds - Series 2019B [Member]
SUBTOTAL LONG-TERM DEBT	21,200	21,200
First Mortgage Bonds - Series 2020A [Member]
SUBTOTAL LONG-TERM DEBT	$ 40,000