Employee Benefit Plans: Funding Status of Employee Benefit Plans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Benefit plan liabilities	$ 152,693	$ 154,472
Pension Plan
Benefit plan liabilities	$ 46,000	$ 51,000

Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant