LONG-TERM DEBT - Long term Debt Outstanding (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Long-term debt
Unamortized debt issuance costs	$ (5,339)	$ (4,490)
Total long-term debt	1,060,986	786,227
Current maturities of long-term debt, net	5,192	5,127
Long-term debt, net	1,055,794	781,100
First Mortgage
Long-term debt
Long-term debt	$ 1,055,454	780,000
First Mortgage Bonds, ZZZ Series, Due 2051
Long-term debt
Interest rate	2.87%
Long-term debt	$ 130,000	0
Frist Mortgage Bonds, Series 1, Due 2061
Long-term debt
Interest rate	3.02%
Long-term debt	$ 150,000	0
First Mortgage Bonds YYY Series Due 2059
Long-term debt
Interest rate	4.17%
Long-term debt	$ 200,000	200,000
First Mortgage Bonds WWW Series Due 2049
Long-term debt
Interest rate	4.07%
Long-term debt	$ 100,000	100,000
First Mortgage Bonds VVV Series Due 2029
Long-term debt
Interest rate	3.40%
Long-term debt	$ 100,000	100,000
First Mortgage Bonds TTT Series Due 2056
Long-term debt
Interest rate	4.61%
Long-term debt	$ 10,000	10,000
First Mortgage Bonds SSS Series Due 2046
Long-term debt
Interest rate	4.41%
Long-term debt	$ 40,000	40,000
First Mortgage Bonds QQQ Series Due 2025
Long-term debt
Interest rate	3.33%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds RRR Series Due 2045
Long-term debt
Interest rate	4.31%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds PPP Series, due 2040
Long-term debt
Interest rate	5.50%
Long-term debt	$ 100,000	100,000
First Mortgage Bonds AAA Series, due in 2025
Long-term debt
Interest rate	7.28%
Long-term debt	$ 20,000	20,000
First Mortgage Bonds BBB Series, due in 2028
Long-term debt
Interest rate	6.77%
Long-term debt	$ 20,000	20,000
First Mortgage Bonds CCC Series, Due 2030
Long-term debt
Interest rate	8.15%
Long-term debt	$ 20,000	20,000
First Mortgage Bonds DDD Series, Due 2031
Long-term debt
Interest rate	7.13%
Long-term debt	$ 20,000	20,000
First Mortgage Bonds EEE Series, Due 2032
Long-term debt
Interest rate	7.11%
Long-term debt	$ 20,000	20,000
First Mortgage Bonds GGG Series, Due 2022
Long-term debt
Interest rate	5.29%
Long-term debt	$ 1,818	3,636
First Mortgage Bonds HHH Series, Due 2022
Long-term debt
Interest rate	5.29%
Long-term debt	$ 1,818	3,636
First Mortgage Bonds III Series, Due 2023
Long-term debt
Interest rate	5.54%
Long-term debt	$ 1,818	2,728
First Mortgage Bonds OOO Series, Due 2031
Long-term debt
Interest rate	6.02%
Long-term debt	$ 20,000	20,000
California Department of Water Resources Loans
Long-term debt
Interest rate	3.00%
Long-term debt	$ 4,832	5,148
Other Long-term Debt
Long-term debt
Long-term debt	$ 6,039	$ 5,569