Loans Receivable Held for Investment - Aging of Recorded Investment in Past Due Loans by Loan Type (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Past due receivable
Total Past Due	$ 391	$ 1,388
Current	338,529	382,669
30-59 Days Past Due
Past due receivable
Total Past Due	341	1,324
60-89 Days Past Due
Past due receivable
Total Past Due	50	64
Single family
Past due receivable
Total Past Due	50	64
Current	111,474	105,268
Single family | 60-89 Days Past Due
Past due receivable
Total Past Due	50	64
Multi-family
Past due receivable
Current	188,918	231,440
Commercial real estate
Past due receivable
Total Past Due		1,324
Current	6,096	7,597
Commercial real estate | 30-59 Days Past Due
Past due receivable
Total Past Due		1,324
Church
Past due receivable
Total Past Due	341
Current	30,171	37,223
Church | 30-59 Days Past Due
Past due receivable
Total Past Due	341
Construction
Past due receivable
Current	1,671	827
Commercial - other
Past due receivable
Current	192	308
Consumer
Past due receivable
Current	$ 7	$ 6