Loans Receivable Held for Investment - Risk Category of Loans by Loan Type (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Credit Quality Indicators
Loans receivable	$ 358,455	$ 338,920
Single family
Credit Quality Indicators
Loans receivable	97,235	111,524
Multi-family
Credit Quality Indicators
Loans receivable	224,404	188,918
Commercial real estate
Credit Quality Indicators
Loans receivable	5,972	6,096
Church
Credit Quality Indicators
Loans receivable	28,587	30,512
Construction
Credit Quality Indicators
Loans receivable	2,048	1,671
Commercial - other
Credit Quality Indicators
Loans receivable	200	192
Consumer
Credit Quality Indicators
Loans receivable	9	7
Pass
Credit Quality Indicators
Loans receivable	351,203	331,712
Pass | Single family
Credit Quality Indicators
Loans receivable	97,186	111,513
Pass | Multi-family
Credit Quality Indicators
Loans receivable	223,455	187,946
Pass | Commercial real estate
Credit Quality Indicators
Loans receivable	5,972	5,974
Pass | Church
Credit Quality Indicators
Loans receivable	22,397	24,474
Pass | Construction
Credit Quality Indicators
Loans receivable	2,048	1,671
Pass | Commercial - other
Credit Quality Indicators
Loans receivable	136	127
Pass | Consumer
Credit Quality Indicators
Loans receivable	9	7
Watch
Credit Quality Indicators
Loans receivable	1,300	813
Watch | Commercial real estate
Credit Quality Indicators
Loans receivable		122
Watch | Church
Credit Quality Indicators
Loans receivable	1,300	691
Special Mention
Credit Quality Indicators
Loans receivable	39
Special Mention | Single family
Credit Quality Indicators
Loans receivable	39
Substandard
Credit Quality Indicators
Loans receivable	5,913	6,395
Substandard | Single family
Credit Quality Indicators
Loans receivable	10	11
Substandard | Multi-family
Credit Quality Indicators
Loans receivable	949	972
Substandard | Church
Credit Quality Indicators
Loans receivable	4,890	5,347
Substandard | Commercial - other
Credit Quality Indicators
Loans receivable	$ 64	$ 65