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CONDENSED CONSOLIDATED STATEMENTS OF CAPITAL STOCK AND LONG-TERM DEBT (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Common Stock, No Par Value	$ 170,562	$ 157,354
Retained Earnings	105,233	91,433
TOTAL COMMON EQUITY	275,795	248,787
TOTAL PREFERRED STOCK	2,084	2,433
SUBTOTAL LONG-TERM DEBT	231,820	162,904
Add: Premium on Issuance of Long-term Debt	8,164	1,259
Less: Unamortized Debt Expense	(4,551)	(3,969)
Less: Current Portion of Long-term Debt	(7,161)	(7,343)
TOTAL LONG-TERM DEBT	228,272	152,851
Amortizing Secured Note, due December 20, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	715	924
Amortizing Secured Note, due May 19, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	3,640	3,955
Amortizing Secured Note, due August 25, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	3,057	3,267
Amortizing Secured Note, due September 19, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	3,337	3,547
State Revolving Trust Note, due December 31, 2022 [Member]
SUBTOTAL LONG-TERM DEBT	202	228
State Revolving Trust Note, due May 1, 2025 [Member]
SUBTOTAL LONG-TERM DEBT	1,519	1,632
State Revolving Trust Note, due March 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	309	351
State Revolving Trust Note, due January 25, 2027 [Member]
SUBTOTAL LONG-TERM DEBT	349	389
State Revolving Trust Note, due December 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	474	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	225	235
State Revolving Trust Note, due January 1, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	73	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	3,343	3,604
Amortizing Secured Note 7.05%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	2,583	2,771
Amortizing Secured Note 5.69%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	5,299	5,684
Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	9,057	9,387
Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	3,361	3,483
State Revolving Trust Note, due July 1, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	1,892	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 30, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	990	1,024
Construction Loans [Member]
SUBTOTAL LONG-TERM DEBT	38,171	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	1,455	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	633	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	2,003	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
0.00%, Series 2018A, due August 1, 2047 [Member]
SUBTOTAL LONG-TERM DEBT	6,678	6,917
3.00%-5.00%, Series 2018B, due August 1, 2047 [Member]
SUBTOTAL LONG-TERM DEBT	2,320	2,365
4.00%, Series 2019A, due August 1, 2059 [Member]
SUBTOTAL LONG-TERM DEBT	32,500
5.00%, Series 2019B, due August 1, 2059 [Member]
SUBTOTAL LONG-TERM DEBT	21,200
Convertible Preferred Stock $7.00 Series [Member]
TOTAL PREFERRED STOCK	1,005	1,005
Convertible Preferred Stock $8.00 Series [Member]
TOTAL PREFERRED STOCK		349
Nonredeemable Preferred Stock $7.00 Series [Member]
TOTAL PREFERRED STOCK	79	79
Nonredeemable Preferred Stock $4.75 Series [Member]
TOTAL PREFERRED STOCK	$ 1,000	$ 1,000

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