Loans Receivable: Non-performing Loans, Foregone interest, and loans committed (Details) - USD ($)		Dec. 31, 2019		Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss	[2]	$ 1,122,238,000	[1]	$ 1,037,429,000	[3]
One-to-four family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		372,528,000		341,966,000
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		172,915,000	[1],[2]	169,355,000	[3]
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		395,152,000	[1],[2]	373,798,000	[3]
Construction Land Development
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		113,665,000	[1],[2]	108,854,000	[3]
Business
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		37,779,000	[1],[2]	30,486,000	[3]
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		30,199,000	[1],[2]	12,970,000	[3]
One-to-four family residential non-owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		161,630,000	[1],[2]	147,825,000	[3]
One-to-four family, residential, owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		210,898,000	[1],[2]	194,141,000	[3]
Performing Financing Receivable
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		1,122,143,000		1,036,677,000
Performing Financing Receivable | One-to-four family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		372,433,000		341,584,000
Performing Financing Receivable | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		172,915,000		169,355,000
Performing Financing Receivable | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		395,152,000		373,472,000
Performing Financing Receivable | Construction Land Development
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		113,665,000		108,854,000
Performing Financing Receivable | Business
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		37,779,000		30,486,000
Performing Financing Receivable | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		30,199,000		12,926,000
Performing Financing Receivable | One-to-four family residential non-owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		161,600,000		147,800,000
Performing Financing Receivable | One-to-four family, residential, owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		210,800,000		193,800,000
Nonperforming Financing Receivable
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		95,000		752,000
Nonperforming Financing Receivable | One-to-four family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		95,000		382,000
Nonperforming Financing Receivable | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		0		0
Nonperforming Financing Receivable | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		0		326,000
Nonperforming Financing Receivable | Construction Land Development
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		0		0
Nonperforming Financing Receivable | Business
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		0		0
Nonperforming Financing Receivable | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		0		44,000
Nonperforming Financing Receivable | One-to-four family residential non-owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		0		0
Nonperforming Financing Receivable | One-to-four family, residential, owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, after Allowance for Credit Loss		$ 95,000		$ 382,000

[1] (1) There were no loans 90 days past due and still accruing interest at December 31, 2018.

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmM4OGZhYWIzOTNiODRlMjdiYjMyMzc3NDdmYzYwZmJifFRleHRTZWxlY3Rpb246NjNERUZGNEVGRTk2MTQ3MUQ1OUExRjAyRTk4MzU1RUMM}

[3] (1) There were no loans 90 days past due and still accruing interest at December 31, 201