FANNIE MAE COMMITMENTS AND PLEDGED SECURITIES - Agency Multifamily Mortgage Based Securities Pledged Securities (Detail) - Agency Mortgage Backed Securities - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments in Agency debt securities
Fair Value	$ 114,941	$ 106,862
Amortized cost	113,586	106,963
Total gains for securities with net gains in AOCI	1,481	77
Total losses for securities with net losses in AOCI	(126)	(178)
Maturities - Fair Value
After one year through five years	941
After five years through ten years	93,586
After ten years	20,414
Total	114,941	106,862
Maturities - Amortized Cost
After one year through five years	917
After five years through ten years	93,686
After ten years	18,983
Total	$ 113,586	$ 106,963