Employee Benefit Plans: Plan Assets Allocation (Details)	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Target Plan Asset Allocations, percent	100.00%	100.00%
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target Plan Asset Allocations, percent	17.00%	26.00%
Real Estate
Defined Benefit Plan Disclosure [Line Items]
Target Plan Asset Allocations, percent	4.00%	4.00%
Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Target Plan Asset Allocations, percent	71.00%	63.00%
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Target Plan Asset Allocations, percent	3.00%	1.00%
Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Target Plan Asset Allocations, percent	5.00%	6.00%