Employee Benefit Plans: Amounts Recognized in the Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-current liability	$ (20,033)	$ (20,981)
Defined Benefit Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Regulatory asset (liability)	19,816	22,717
Current liability	0	0
Non-current liability	(11,236)	(12,080)
Supplemental Non-qualified Defined Benefit Retirement Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Regulatory asset (liability)	0	0
Current liability	(216)	(217)
Non-current liability	(3,210)	(3,382)
Non-pension Defined Benefit Postretirement Healthcare Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Regulatory asset (liability)	(1,946)	2,306
Current liability	(619)	(519)
Non-current liability	$ (5,587)	$ (5,519)