REVENUES: Receivables and Allowance for Uncollectible Accounts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 5,034	$ 4,499
Additions to the allowance	577	488
Write-offs, net of recoveries	(549)	(137)
Balance at end of period	$ 5,062	$ 4,850
Allowance for uncollectible accounts as a percentage of customer receivables	4.80%	5.60%