Loans Receivable Held for Investment - Risk Category of Loans by Loan Type (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Credit Quality Indicators
Loans receivable	$ 350,401	$ 338,920
Single family
Credit Quality Indicators
Loans receivable	108,870	111,524
Multi-family
Credit Quality Indicators
Loans receivable	204,493	188,918
Commercial real estate
Credit Quality Indicators
Loans receivable	5,826	6,096
Church
Credit Quality Indicators
Loans receivable	29,921	30,512
Construction
Credit Quality Indicators
Loans receivable	1,092	1,671
Commercial - other
Credit Quality Indicators
Loans receivable	195	192
Consumer
Credit Quality Indicators
Loans receivable	4	7
Pass
Credit Quality Indicators
Loans receivable	343,303	331,712
Pass | Single family
Credit Quality Indicators
Loans receivable	108,859	111,513
Pass | Multi-family
Credit Quality Indicators
Loans receivable	203,528	187,946
Pass | Commercial real estate
Credit Quality Indicators
Loans receivable	5,704	5,974
Pass | Church
Credit Quality Indicators
Loans receivable	23,985	24,474
Pass | Construction
Credit Quality Indicators
Loans receivable	1,092	1,671
Pass | Commercial - other
Credit Quality Indicators
Loans receivable	131	127
Pass | Consumer
Credit Quality Indicators
Loans receivable	4	7
Watch
Credit Quality Indicators
Loans receivable	808	813
Watch | Commercial real estate
Credit Quality Indicators
Loans receivable	122	122
Watch | Church
Credit Quality Indicators
Loans receivable	686	691
Substandard
Credit Quality Indicators
Loans receivable	6,290	6,395
Substandard | Single family
Credit Quality Indicators
Loans receivable	11	11
Substandard | Multi-family
Credit Quality Indicators
Loans receivable	965	972
Substandard | Church
Credit Quality Indicators
Loans receivable	5,250	5,347
Substandard | Commercial - other
Credit Quality Indicators
Loans receivable	$ 64	$ 65