Business Description and Summary of Significant Accounting Policies: Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Schedule Of Regulatory Assets And Liabilities [Line Items]
Deferred income tax liabilities, net, non-current		$ 188,961	$ 193,042
Regulatory Assets		85,813	78,684
Regulatory Liabilities		$ 51,583	54,989
Cost of removal for utility plant [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities, Maximum Recovery Period		53 years
Regulatory Liabilities	[1]	$ 38,131	35,510
Employee benefit plans [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities, Maximum Recovery Period		12 years
Regulatory Liabilities	[2]	$ 12,616	14,538
Other regulatory liabilities [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities, Maximum Recovery Period		13 years
Regulatory Liabilities	[2]	$ 836	4,941
Unamortized loss on reacquired debt [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Maximum Recovery Period		9 years
Regulatory Assets	[1]	$ 2,096	2,377
Allowance for Funds Used During Construction [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Maximum Recovery Period		45 years
Regulatory Assets	[3]	$ 8,571	8,365
Employee benefit plans [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Maximum Recovery Period		12 years
Regulatory Assets	[2]	$ 20,866	24,418
Deferred energy costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Maximum Recovery Period		1 year
Regulatory Assets	[1]	$ 19,875	14,696
Flow through accounting [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Maximum Recovery Period		35 years
Regulatory Assets	[1]	$ 12,104	11,171
Decommissioning costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Maximum Recovery Period		9 years
Regulatory Assets	[1]	$ 13,686	11,786
Other Regulatory Assets [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Maximum Recovery Period		2 years
Regulatory Assets	[1],[4]	$ 8,615	$ 5,871
Vegetation Management [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	[1],[4]	$ 5,000

[1] Recovery of costs but we are not allowed a rate of return.

[2] In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base, respectively.

[3] In addition to recovery of costs, we are allowed a rate of return.

[4] Includes approximately $5.0 million of vegetation management expenses.