Loans Receivable Held for Investment - Aging of Recorded Investment in Past Due Loans by Loan Type (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Past due receivable
Total Past Due	$ 39	$ 391
Current	358,416	338,529
Gross loans receivable after deferred loan costs and premiums	358,455	338,920
30-59 Days Past Due
Past due receivable
Total Past Due	39	341
60-89 Days Past Due
Past due receivable
Total Past Due		50
Single family
Past due receivable
Total Past Due	39	50
Current	97,196	111,474
Gross loans receivable after deferred loan costs and premiums	97,235	111,524
Single family | 30-59 Days Past Due
Past due receivable
Total Past Due	39
Single family | 60-89 Days Past Due
Past due receivable
Total Past Due		50
Multi-family
Past due receivable
Current	224,404	188,918
Gross loans receivable after deferred loan costs and premiums	224,404	188,918
Commercial real estate
Past due receivable
Current	5,972	6,096
Gross loans receivable after deferred loan costs and premiums	5,972	6,096
Church
Past due receivable
Total Past Due		341
Current	28,587	30,171
Gross loans receivable after deferred loan costs and premiums	28,587	30,512
Church | 30-59 Days Past Due
Past due receivable
Total Past Due		341
Construction
Past due receivable
Current	2,048	1,671
Gross loans receivable after deferred loan costs and premiums	2,048	1,671
Commercial - other
Past due receivable
Current	200	192
Gross loans receivable after deferred loan costs and premiums	200	192
Consumer
Past due receivable
Current	9	7
Gross loans receivable after deferred loan costs and premiums	$ 9	$ 7