Employee Benefit Plans: Defined Benefit Plans Assumptions (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Expected long-term rate of return on assets		6.75%	6.75%
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
1% Increase on Service and Interest Costs		$ 10
1% Increase on Accumulated Periodic Postretirement Benefit Obligation		221
1% Decrease on Service and Interest Cost		(1)
1% Decrease on Accumulated Periodic Postretirement Benefit Obligation		$ (205)
Defined Benefit Pension Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate		4.63%	4.25%	5.10%
Rate of increase in compensation levels		3.57%	3.86%	3.86%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate		4.25%	5.10%	4.35%
Expected long-term rate of return on assets	[1]	6.75%	6.75%	7.25%
Rate of increase in compensation levels		3.86%	3.86%	3.91%
Defined Benefit Plan Assumptions Used In Calculating Net Periodic Benefit Cost Expected Rate of Return On Assets For Next Fiscal Year		6.75%
Supplemental Non-qualified Defined Benefit Retirement Plans [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate		4.29%	3.98%	4.68%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate		3.98%	4.68%	3.88%
Non-pension Defined Benefit Postretirement Healthcare Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate		4.03%	3.70%	4.45%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate		3.70%	4.45%	3.65%
Healthcare trend rate pre-65 [Member]
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Trend for next year		6.35%	7.50%
Ultimate trend rate		4.50%	4.50%
Year Ultimate Trend Reached		2024	2027
Healthcare trend rate post-65 [Member]
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Trend for next year		5.20%	6.25%
Ultimate trend rate		4.50%	4.50%
Year Ultimate Trend Reached		2023	2024

[1] The expected rate of return on plan assets is 6.75% for the calculation of the 2016 net periodic pension cost.