Regulatory Matters: Regulatory Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 160,080	$ 166,171
Less current regulatory liabilities	0	(3,162)
Regulatory liabilities, non-current	160,080	163,009
Cost of removal for utility plant
Regulatory Liabilities [Line Items]
Total regulatory liabilities	56,558	57,318
Employee benefit plan costs and related deferred taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	6,986	7,023
Excess deferred income taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	95,770	98,228
Other regulatory liabilities
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 766	$ 3,602