CONDENSED CONSOLIDATED STATEMENTS OF CAPITAL STOCK AND LONG-TERM DEBT (Unaudited) (Parenthetical) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Common Stock, Shares Authorized	40,000	40,000
Common Stock, Shares Outstanding	16,554	16,403
Preferred Stock, Shares Authorized	126	126
Preferred Stock, Shares Outstanding	23	23
Due date of debt	Sep. 30, 2019
State Revolving Trust Note, due February 1, 2036 [Member]
Interest rate	2.00%
Due date of debt	Feb. 01, 2036
Convertible Preferred Stock $7.00 Series [Member]
Preferred Stock, Shares Outstanding	10	10
Convertible Preferred Stock $8.00 Series [Member]
Preferred Stock, Shares Outstanding	3	3
Nonredeemable Preferred Stock $7.00 Series [Member]
Preferred Stock, Shares Outstanding	1	1
Nonredeemable Preferred Stock $4.75 Series [Member]
Preferred Stock, Shares Outstanding	10	10
Amortizing Secured Note, due December 20, 2021 [Member]
Interest rate	8.05%
Due date of debt	Dec. 20, 2021
Amortizing Secured Note, due May 19, 2028 [Member]
Interest rate	6.25%
Due date of debt	May 19, 2028
Amortizing Secured Note, due August 25, 2030 [Member]
Interest rate	6.44%
Due date of debt	Aug. 25, 2030
Amortizing Secured Note, due September 19, 2031 [Member]
Interest rate	6.46%
Due date of debt	Sep. 19, 2031
State Revolving Trust Note, due December 31, 2022 [Member]
Interest rate	4.22%
Due date of debt	Dec. 31, 2022
State Revolving Trust Note, due May 1, 2025 [Member]
Interest rate	3.60%
Due date of debt	May 01, 2025
State Revolving Trust Note, due March 1, 2026 [Member]
Interest rate	3.30%
Due date of debt	Mar. 01, 2026
State Revolving Trust Note, due January 25, 2027 [Member]
Interest rate	3.49%
Due date of debt	Jan. 25, 2027
State Revolving Trust Note, due December 1, 2026 [Member]
Interest rate	4.03%
Due date of debt	Dec. 01, 2026
State Revolving Trust Bond 4.00% to 5.00%, due August 1, 2021 [Member]
Due date of debt	Aug. 01, 2021
State Revolving Trust Bond 4.00% to 5.00%, due August 1, 2021 [Member] | Minimum [Member]
Interest rate	4.00%
State Revolving Trust Bond 4.00% to 5.00%, due August 1, 2021 [Member] | Maximum [Member]
Interest rate	5.00%
State Revolving Fund Bond 0.00%, due August 1, 2021 [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2021
State Revolving Trust Note, due July 1, 2028 [Member]
Interest rate	3.64%
Due date of debt	Jul. 01, 2028
State Revolving Trust Note, due January 1, 2028 [Member]
Interest rate	3.64%
Due date of debt	Jan. 01, 2028
State Revolving Trust Note, due August 1, 2031 [Member]
Interest rate	3.45%
Due date of debt	Aug. 01, 2031
Amortizing Secured Note, due April 20, 2029 [Member]
Interest rate	6.59%
Due date of debt	Apr. 20, 2029
Amortizing Secured Note 7.05%, due January 20, 2030 [Member]
Interest rate	7.05%
Due date of debt	Jan. 20, 2030
Amortizing Secured Note 5.69%, due January 20, 2030 [Member]
Interest rate	5.69%
Due date of debt	Jan. 20, 2030
Amortizing Secured Note, due April 20, 2040 [Member]
Interest rate	4.45%
Due date of debt	Apr. 20, 2040
Amortizing Secured Note, due April 20, 2040 [Member]
Interest rate	4.47%
Due date of debt	Apr. 20, 2040
State Revolving Trust Note, due July 1, 2031 [Member]
Interest rate	3.75%
Due date of debt	Jul. 01, 2031
State Revolving Trust Note, due November 30, 2030 [Member]
Interest rate	3.75%
Due date of debt	Nov. 30, 2030
First Mortgage Bonds - Series X [Member]
Interest rate	0.00%
First Mortgage Bonds - Series Z [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2019
First Mortgage Bonds - Series AA [Member]
Due date of debt	Aug. 01, 2019
First Mortgage Bonds - Series AA [Member] | Minimum [Member]
Interest rate	5.25%
First Mortgage Bonds - Series AA [Member] | Maximum [Member]
Interest rate	5.75%
First Mortgage Bonds - Series BB [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2021
First Mortgage Bonds - Series CC [Member]
Due date of debt	Aug. 01, 2021
First Mortgage Bonds - Series CC [Member] | Minimum [Member]
Interest rate	4.00%
First Mortgage Bonds - Series CC [Member] | Maximum [Member]
Interest rate	5.00%
First Mortgage Bonds - Series EE [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2023
First Mortgage Bonds - Series FF [Member]
Due date of debt	Aug. 01, 2024
First Mortgage Bonds - Series FF [Member] | Minimum [Member]
Interest rate	3.00%
First Mortgage Bonds - Series FF [Member] | Maximum [Member]
Interest rate	5.50%
First Mortgage Bonds - Series GG [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2026
First Mortgage Bonds - Series HH [Member]
Due date of debt	Aug. 01, 2026
First Mortgage Bonds - Series HH [Member] | Minimum [Member]
Interest rate	4.00%
First Mortgage Bonds - Series HH [Member] | Maximum [Member]
Interest rate	5.00%
First Mortgage Bonds - Series II [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2024
First Mortgage Bonds - Series JJ [Member]
Due date of debt	Aug. 01, 2027
First Mortgage Bonds - Series JJ [Member] | Minimum [Member]
Interest rate	3.40%
First Mortgage Bonds - Series JJ [Member] | Maximum [Member]
Interest rate	5.00%
First Mortgage Bonds - Series KK [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2028
First Mortgage Bonds - Series LL [Member]
Due date of debt	Aug. 01, 2028
First Mortgage Bonds - Series LL [Member] | Minimum [Member]
Interest rate	5.00%
First Mortgage Bonds - Series LL [Member] | Maximum [Member]
Interest rate	5.50%
First Mortgage Bonds - Series MM [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2030
First Mortgage Bonds - Series NN [Member]
Due date of debt	Aug. 01, 2030
First Mortgage Bonds - Series NN [Member] | Minimum [Member]
Interest rate	3.00%
First Mortgage Bonds - Series NN [Member] | Maximum [Member]
Interest rate	4.375%
First Mortgage Bonds - Series OO [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2031
First Mortgage Bonds - Series PP [Member]
Due date of debt	Aug. 01, 2031
First Mortgage Bonds - Series PP [Member] | Minimum [Member]
Interest rate	2.00%
First Mortgage Bonds - Series PP [Member] | Maximum [Member]
Interest rate	5.00%
First Mortgage Bonds - Series QQ [Member]
Interest rate	5.00%
Due date of debt	Oct. 01, 2023
First Mortgage Bonds - Series RR [Member]
Interest rate	3.80%
Due date of debt	Oct. 01, 2038
First Mortgage Bonds - Series SS [Member]
Interest rate	4.25%
Due date of debt	Oct. 01, 2047
First Mortgage Bonds - Series TT [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2032
First Mortgage Bonds - Series UU [Member]
Due date of debt	Aug. 01, 2032
First Mortgage Bonds - Series UU [Member] | Minimum [Member]
Interest rate	3.00%
First Mortgage Bonds - Series UU [Member] | Maximum [Member]
Interest rate	3.25%
First Mortgage Bonds - Series VV [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2033
First Mortgage Bonds - Series WW [Member]
Due date of debt	Aug. 01, 2033
First Mortgage Bonds - Series WW [Member] | Minimum [Member]
Interest rate	3.00%
First Mortgage Bonds - Series WW [Member] | Maximum [Member]
Interest rate	5.00%
First Mortgage Bonds - Series XX [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2047
First Mortgage Bonds - Series YY [Member]
Due date of debt	Aug. 01, 2047
First Mortgage Bonds - Series YY [Member] | Minimum [Member]
Interest rate	3.00%
First Mortgage Bonds - Series YY [Member] | Maximum [Member]
Interest rate	5.00%
0.00%, Series 2018A, due August 1, 2047 [Member]
Interest rate	0.00%
Due date of debt	Aug. 01, 2047
3.00%-5.00%, Series 2018B, due August 1, 2047 [Member]
Due date of debt	Aug. 01, 2047
3.00%-5.00%, Series 2018B, due August 1, 2047 [Member] | Minimum [Member]
Interest rate	3.00%
3.00%-5.00%, Series 2018B, due August 1, 2047 [Member] | Maximum [Member]
Interest rate	5.00%
Construction Loans [Member]
Interest rate	0.00%