Loans Receivable Held for Investment - Risk Category of Loans by Loan Type (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Credit Quality Indicators
Loans receivable	$ 368,991	$ 338,920
Single family
Credit Quality Indicators
Loans receivable	100,017	111,524
Multi-family
Credit Quality Indicators
Loans receivable	231,669	188,918
Commercial real estate
Credit Quality Indicators
Loans receivable	6,007	6,096
Church
Credit Quality Indicators
Loans receivable	29,329	30,512
Construction
Credit Quality Indicators
Loans receivable	1,761	1,671
Commercial - other
Credit Quality Indicators
Loans receivable	201	192
Consumer
Credit Quality Indicators
Loans receivable	7	7
Pass
Credit Quality Indicators
Loans receivable	360,497	331,712
Pass | Single family
Credit Quality Indicators
Loans receivable	100,007	111,513
Pass | Multi-family
Credit Quality Indicators
Loans receivable	228,897	187,946
Pass | Commercial real estate
Credit Quality Indicators
Loans receivable	6,007	5,974
Pass | Church
Credit Quality Indicators
Loans receivable	23,681	24,474
Pass | Construction
Credit Quality Indicators
Loans receivable	1,761	1,671
Pass | Commercial - other
Credit Quality Indicators
Loans receivable	137	127
Pass | Consumer
Credit Quality Indicators
Loans receivable	7	7
Watch
Credit Quality Indicators
Loans receivable	2,496	813
Watch | Multi-family
Credit Quality Indicators
Loans receivable	1,815
Watch | Commercial real estate
Credit Quality Indicators
Loans receivable		122
Watch | Church
Credit Quality Indicators
Loans receivable	681	691
Substandard
Credit Quality Indicators
Loans receivable	5,998	6,395
Substandard | Single family
Credit Quality Indicators
Loans receivable	11	11
Substandard | Multi-family
Credit Quality Indicators
Loans receivable	957	972
Substandard | Church
Credit Quality Indicators
Loans receivable	4,966	5,347
Substandard | Commercial - other
Credit Quality Indicators
Loans receivable	$ 64	$ 65