CONSOLIDATED STATEMENTS OF CAPITAL STOCK AND LONG-TERM DEBT - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Common Stock, No Par Value	$ 215,125	$ 157,354
Retained Earnings	108,667	91,433
TOTAL COMMON EQUITY	323,792	248,787
TOTAL PREFERRED STOCK	2,084	2,433
SUBTOTAL LONG-TERM DEBT	234,397	162,904
Add: Premium on Issuance of Long-term Debt	8,064	1,259
Less: Unamortized Debt Expense	(4,506)	(3,969)
Less: Current Portion of Long-term Debt	(7,178)	(7,343)
TOTAL LONG-TERM DEBT	230,777	152,851
Convertible Preferred Stock $7.00 Series
SUBTOTAL LONG-TERM DEBT	1,005	1,005
Convertible Preferred Stock $8.00 Series [Member]
SUBTOTAL LONG-TERM DEBT		349
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	643	924
Amortizing Secured Note, due May 19, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	3,535	3,955
Amortizing Secured Note, due August 25, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	2,987	3,267
Amortizing Secured Note, due September 19, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	3,267	3,547
State Revolving Trust Note, due December 31, 2022 [Member]
SUBTOTAL LONG-TERM DEBT	175	228
State Revolving Trust Note, due May 1, 2025 [Member]
SUBTOTAL LONG-TERM DEBT	1,405	1,632
State Revolving Trust Note, due March 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	309	351
State Revolving Trust Note2 [Member]
SUBTOTAL LONG-TERM DEBT	349	389
State Revolving Trust Note, due December 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	446	501
State Revolving Trust Bond 4.00% to 5.00%, due August 1, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	60	111
State Revolving Trust Bond 0.00%, due August 1, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	50	88
State Revolving Trust Note, due July 1, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	214	235
State Revolving Trust Note, due January 1, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	69	77
State Revolving Trust Note, due August 1, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	851	907
Amortizing Secured Note, due April 20, 2029 [Member]
SUBTOTAL LONG-TERM DEBT	3,255	3,604
Amortizing Secured Note 7.05%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	2,521	2,771
Amortizing Secured Note 5.69%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	5,171	5,684
4.45%, Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	8,946	9,387
4.47%, Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	3,320	3,483
State Revolving Trust Note, due July 1, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	1,829	1,954
State Revolving Trust Note, due February 1, 2036 [Member]
SUBTOTAL LONG-TERM DEBT	1,013	1,064
State Revolving Trust Note, due November 1, 2038 [Member]
SUBTOTAL LONG-TERM DEBT	1,309
State Revolving Trust Note, due November 30, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	955	1,024
Construction Loans [Member]
SUBTOTAL LONG-TERM DEBT	40,467	16,509
First Mortgage Bonds - Series Z [Member]
SUBTOTAL LONG-TERM DEBT		113
First Mortgage Bonds - Series AA [Member]
SUBTOTAL LONG-TERM DEBT		155
First Mortgage Bonds - Series BB [Member]
SUBTOTAL LONG-TERM DEBT	241	362
First Mortgage Bonds - Series CC [Member]
SUBTOTAL LONG-TERM DEBT	331	489
First Mortgage Bonds - Series EE [Member]
SUBTOTAL LONG-TERM DEBT	1,456	1,876
First Mortgage Bonds - Series FF [Member]
SUBTOTAL LONG-TERM DEBT	2,440	2,980
First Mortgage Bonds - Series GG [Member]
SUBTOTAL LONG-TERM DEBT	632	723
First Mortgage Bonds - Series HH [Member]
SUBTOTAL LONG-TERM DEBT	710	795
First Mortgage Bonds - Series II [Member]
SUBTOTAL LONG-TERM DEBT	429	520
First Mortgage Bonds - Series JJ [Member]
SUBTOTAL LONG-TERM DEBT	588	671
First Mortgage Bonds - Series KK [Member]
SUBTOTAL LONG-TERM DEBT	807	898
First Mortgage Bonds - Series LL [Member]
SUBTOTAL LONG-TERM DEBT	928	1,010
First Mortgage Bonds - Series MM [Member]
SUBTOTAL LONG-TERM DEBT	1,037	1,137
First Mortgage Bonds - Series NN [Member]
SUBTOTAL LONG-TERM DEBT	1,190	1,415
First Mortgage Bonds - Series OO [Member]
SUBTOTAL LONG-TERM DEBT	1,806	1,956
First Mortgage Bonds - Series PP [Member]
SUBTOTAL LONG-TERM DEBT	660	700
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	1,957	2,107
First Mortgage Bonds - Series UU [Member]
SUBTOTAL LONG-TERM DEBT	755	800
First Mortgage Bonds - Series VV [Member]
SUBTOTAL LONG-TERM DEBT	2,004	2,147
First Mortgage Bonds - Series WW [Member]
SUBTOTAL LONG-TERM DEBT	755	795
First Mortgage Bonds - Series XX [Member]
SUBTOTAL LONG-TERM DEBT	10,627	11,006
First Mortgage Bonds - Series YY [Member]
SUBTOTAL LONG-TERM DEBT	3,785	3,860
First Mortgage Bonds - Series 2018A [Member]
SUBTOTAL LONG-TERM DEBT	6,678	6,917
First Mortgage Bonds - Series 2018B [Member]
SUBTOTAL LONG-TERM DEBT	2,320	2,365
First Mortgage Bonds - Series 2019A [Member]
SUBTOTAL LONG-TERM DEBT	32,500
First Mortgage Bonds - Series 2019B [Member]
SUBTOTAL LONG-TERM DEBT	$ 21,200