CONDENSED CONSOLIDATED STATEMENTS OF CAPITAL STOCK AND LONG-TERM DEBT - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Common Stock, No Par Value	$ 154,075	$ 153,045
Retained Earnings	68,249	65,392
TOTAL COMMON EQUITY	222,324	218,437
TOTAL PREFERRED STOCK	2,435	2,436
SUBTOTAL LONG-TERM DEBT	144,421	142,489
Add: Premium on Issuance of Long-term Debt	1,388	1,495
Less: Unamortized Debt Expense	(3,216)	(3,287)
Less: Current Portion of Long-term Debt	(6,164)	(6,159)
TOTAL LONG-TERM DEBT	136,429	134,538
First Mortgage Bonds - Series WW [Member]
SUBTOTAL LONG-TERM DEBT	865	865
First Mortgage Bonds - Series VV [Member]
SUBTOTAL LONG-TERM DEBT	2,386	2,433
First Mortgage Bonds - Series UU [Member]
SUBTOTAL LONG-TERM DEBT	890	890
First Mortgage Bonds - Series TT [Member]
SUBTOTAL LONG-TERM DEBT	2,358	2,408
First Mortgage Bonds - Series SS [Member]
SUBTOTAL LONG-TERM DEBT	23,000	23,000
First Mortgage Bonds - Series RR [Member]
SUBTOTAL LONG-TERM DEBT	22,500	22,500
First Mortgage Bonds - Series QQ [Member]
SUBTOTAL LONG-TERM DEBT	9,915	9,915
First Mortgage Bonds - Series PP [Member]
SUBTOTAL LONG-TERM DEBT	780	780
First Mortgage Bonds - Series OO [Member]
SUBTOTAL LONG-TERM DEBT	2,207	2,258
First Mortgage Bonds - Series NN [Member]
SUBTOTAL LONG-TERM DEBT	1,590	1,590
First Mortgage Bonds - Series MM [Member]
SUBTOTAL LONG-TERM DEBT	1,304	1,337
First Mortgage Bonds - Series LL [Member]
SUBTOTAL LONG-TERM DEBT	1,175	1,175
First Mortgage Bonds - Series JJ [Member]
SUBTOTAL LONG-TERM DEBT	824	824
First Mortgage Bonds - Series KK [Member]
SUBTOTAL LONG-TERM DEBT	1,058	1,078
First Mortgage Bonds - Series HH [Member]
SUBTOTAL LONG-TERM DEBT	960	960
First Mortgage Bonds - Series II [Member]
SUBTOTAL LONG-TERM DEBT	683	700
First Mortgage Bonds - Series GG [Member]
SUBTOTAL LONG-TERM DEBT	887	903
First Mortgage Bonds - Series EE [Member]
SUBTOTAL LONG-TERM DEBT	2,641	2,713
First Mortgage Bonds - Series FF [Member]
SUBTOTAL LONG-TERM DEBT	3,690	3,690
First Mortgage Bonds - Series BB [Member]
SUBTOTAL LONG-TERM DEBT	590	603
First Mortgage Bonds - Series CC [Member]
SUBTOTAL LONG-TERM DEBT	779	779
First Mortgage Bonds - Series AA [Member]
SUBTOTAL LONG-TERM DEBT	440	440
First Mortgage Bonds - Series Y [Member]
SUBTOTAL LONG-TERM DEBT	123	122
First Mortgage Bonds - Series Z [Member]
SUBTOTAL LONG-TERM DEBT	329	336
State Revolving Trust Note, due November 30, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	1,123	1,154
First Mortgage Bonds - Series X [Member]
SUBTOTAL LONG-TERM DEBT	105	107
Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	10,047	10,267
State Revolving Trust Note, due July 1, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	2,133	2,191
Amortizing Secured Note 7.05%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	3,146	3,271
Amortizing Secured Note 5.69%, due January 20, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	6,453	6,709
State Revolving Trust Note, due August 1, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	989	1,015
Amortizing Secured Note, due April 20, 2029 [Member]
SUBTOTAL LONG-TERM DEBT	4,127	4,302
State Revolving Trust Note, due July 1, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	266	276
State Revolving Trust Note, due January 1, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	87	91
State Revolving Trust Bond 4.00% to 5.00%, due August 1, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	213	213
State Revolving Trust Bond 0.00%, due August 1, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	162	166
State Revolving Trust Note, due January 25, 2027 [Member]
SUBTOTAL LONG-TERM DEBT	446	465
State Revolving Trust Note, due December 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	578	603
State Revolving Trust Note, due May 1, 2025 [Member]
SUBTOTAL LONG-TERM DEBT	1,958	2,062
State Revolving Trust Note, due March 1, 2026 [Member]
SUBTOTAL LONG-TERM DEBT	411	431
Amortizing Secured Note, due September 19, 2031 [Member]
SUBTOTAL LONG-TERM DEBT	3,967	4,107
State Revolving Trust Note, due December 31, 2022 [Member]
SUBTOTAL LONG-TERM DEBT	304	329
Amortizing Secured Note, due May 19, 2028 [Member]
SUBTOTAL LONG-TERM DEBT	4,585	4,795
Amortizing Secured Note, due August 25, 2030 [Member]
SUBTOTAL LONG-TERM DEBT	3,687	3,827
Amortizing Secured Note, due December 20, 2021 [Member]
SUBTOTAL LONG-TERM DEBT	1,300	1,415
Construction Loans [Member]
SUBTOTAL LONG-TERM DEBT	11,517	7,470
Amortizing Secured Note, due April 20, 2040 [Member]
SUBTOTAL LONG-TERM DEBT	3,728	3,809
Convertible Preferred Stock $7.00 Series [Member]
TOTAL PREFERRED STOCK	1,007	1,007
Convertible Preferred Stock $8.00 Series [Member]
TOTAL PREFERRED STOCK	349	349
Nonredeemable Preferred Stock $7.00 Series [Member]
TOTAL PREFERRED STOCK	79	80
Nonredeemable Preferred Stock $4.75 Series [Member]
TOTAL PREFERRED STOCK	1,000	1,000
State Revolving Trust Note, due February 1, 2036 [Member]
TOTAL PREFERRED STOCK	$ 1,115	$ 1,115