OTHER INCOME AND EXPENSES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other income and expenses
Revenue from contracts with customers	$ 765,704	$ 697,577	$ 664,358
Change in value of life insurance contracts gain	(3,800)	(4,293)	(5,104)
Nonoperating expense	17,234	14,300	13,869
Revenue	22,761	16,922	19,205
Expense	17,234	14,300	13,869
Operating and maintenance revenue
Other income and expenses
Revenue from contracts with customers	16,276	11,481	12,655
Expense from contract with customer	16,344	13,551	13,791
Leases
Other income and expenses
Lease revenue	2,744	2,398	2,279
Lease expense	230	48	35
Design and construction
Other income and expenses
Revenue from contracts with customers	619	802	1,745
Expense from contract with customer	611	704	1,612
Meter reading and billing
Other income and expenses
Revenue from contracts with customers	495	458	412
Expense from contract with customer	79	109	163
Interest income
Other income and expenses
Interest income	171	52	92
Other non-regulated income and expenses
Other income and expenses
Nonoperating income	2,456	1,731	2,022
Nonoperating expense	$ 3,770	$ 4,181	$ 3,372