Fair Value Measurements: Fair Value Measurements, Nonrecurring, Valuation Techniques (Details) - Nonrecurring - Fair Value, Inputs, Level 3 - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Assets, estimated fair value, nonrecurring	$ 2,123	$ 2,211
Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Assets, estimated fair value, nonrecurring	464	528
Impaired loans | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Assets, estimated fair value, nonrecurring	464	528
OREO and other repossessed assets | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Assets, estimated fair value, nonrecurring	$ 1,659	$ 1,683