FANNIE MAE COMMITMENTS AND PLEDGED SECURITIES - Agency Multifamily Mortgage Based Securities Pledged Securities (Detail) - Agency Mortgage Backed Securities $ in Thousands	Mar. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($)
Investments in Agency debt securities
Fair Value	$ 112,952	$ 114,563
Amortized cost	114,528	113,580
Total gains for securities with net gains in AOCI	17	1,145
Total losses for securities with net losses in AOCI	(1,593)	(162)
Fair value of securities with unrealized losses	$ 85,974	66,526
Pledged securities in a continuous unrealized loss position for more than 12 months | security	0
Maturities - Fair Value
After one year through five years	$ 2,605
After five years through ten years	94,860
After ten years	15,487
Total	112,952	114,563
Maturities - Amortized Cost
After one year through five years	2,630
After five years through ten years	95,159
After ten years	16,739
Total	$ 114,528	$ 113,580