Employee Benefit Plans: Narrative (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Measurement Date		December 31
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets		6.75%	6.75%
Defined Benefit Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unfunded Status of Plan		$ (11.0)
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	[1]	6.75%	6.75%	7.25%
Non-pension Defined Benefit Postretirement Healthcare Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unfunded Status of Plan		$ (6.2)
Supplemental Non-qualified Defined Benefit Retirement Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unfunded Status of Plan		$ (3.4)

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