Loans Receivable Held for Investment - Aging of Recorded Investment in Past Due Loans by Loan Type (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Past due receivable
Total Past Due	$ 102	$ 391
Current	350,299	338,529
Gross loans receivable after deferred loan costs and premiums	350,401	338,920
30-59 Days Past Due
Past due receivable
Total Past Due	56	341
60-89 Days Past Due
Past due receivable
Total Past Due	46	50
Single family
Past due receivable
Total Past Due	102	50
Current	108,768	111,474
Gross loans receivable after deferred loan costs and premiums	108,870	111,524
Single family | 30-59 Days Past Due
Past due receivable
Total Past Due	56
Single family | 60-89 Days Past Due
Past due receivable
Total Past Due	46	50
Multi-family
Past due receivable
Current	204,493	188,918
Gross loans receivable after deferred loan costs and premiums	204,493	188,918
Commercial real estate
Past due receivable
Current	5,826	6,096
Gross loans receivable after deferred loan costs and premiums	5,826	6,096
Church
Past due receivable
Total Past Due		341
Current	29,921	30,171
Gross loans receivable after deferred loan costs and premiums	29,921	30,512
Church | 30-59 Days Past Due
Past due receivable
Total Past Due		341
Construction
Past due receivable
Current	1,092	1,671
Gross loans receivable after deferred loan costs and premiums	1,092	1,671
Commercial - other
Past due receivable
Current	195	192
Gross loans receivable after deferred loan costs and premiums	195	192
Consumer
Past due receivable
Current	4	7
Gross loans receivable after deferred loan costs and premiums	$ 4	$ 7