Summarized Quarterly Results (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Interest-Agency MBS	$ 19,990	$ 20,335	$ 24,137	$ 25,711					$ 90,173	$ 95,656	$ 76,657
Interest-Agency MBS					$ 23,208	$ 23,578	$ 24,814	$ 24,044
Interest-Non-Agency MBS	8,614	9,299	9,659	10,466					38,038	40,733	38,266
Interest-Non-Agency MBS					10,445	10,377	9,902	10,021
Interest-residential mortgage loans	4,767	5,049	5,259	5,368	5,519	5,750	5,955	6,238	20,443	23,463	27,720
Interest-residential mortgage loans held-for-securitization	1,618	1,574	1,036	86					4,314
Other interest income					29	20	44	28	1,427	120	105
Other interest income	253	679	20	19
Interest and Dividend Income, Operating, Total					39,201	39,725	40,715	40,331	154,395	159,972	142,748
Interest and Dividend Income, Operating, Total	35,242	36,936	40,111	41,650
Interest expense:
Interest expense on repurchase agreements	18,489	21,132	25,979	27,136	25,362	24,027	22,028	19,093	92,737	90,511	53,954
Interest expense on asset-backed securities	4,600	4,880	5,091	5,200	5,351	5,581	5,797	6,070	19,771	22,800	26,939
Interest expense on warehouse line of credit	1,477	1,381	1,057	234					4,148
Interest expense on junior subordinated notes	492	520	542	547	526	519	504	447	2,100	1,996	1,626
Interest Expense, Total	25,058	27,913	32,669	33,117	31,239	30,127	28,329	25,610	118,756	115,307	82,519
Net interest income					7,962	9,598	12,386	14,721	35,639	44,665	60,229
Net interest income	10,184	9,023	7,442	8,533
Total operating expenses					(3,675)	(3,199)	(3,395)	(3,233)	(13,306)	(13,503)	(13,305)
Total operating expenses	3,263	3,258	3,113	3,046
Other (loss) income:
Income-rental properties	441	469	453	436	428	436	445	451	1,800	1,761	1,710
Realized net gain (loss) on sale of MBS	1,338	214	444	(6,147)	(999)	799		(11,987)
Realized net (loss) gain on sale of Agency MBS held as trading investments	1,342		234	(7,363)	(3,871)	(231)		(7,327)
Impairment charge on Non-Agency MBS	(357)	(1,145)	(606)		(971)	(141)	(1,757)		(2,108)	(2,869)	(2,399)
Unrealized gain (loss) on Agency MBS held as trading investments	(798)	1,939	989	14,906	9,674	(3,017)	(2,677)	(8,890)
Gain (loss) on sale of residential properties	31				23	30			31	54
(Loss) gain on derivatives, net	20,824	(24,734)	(53,543)	(27,289)	(44,504)	13,090	9,930	13,412	(84,741)	(8,071)	7,132
Recovery on Non-Agency MBS							1			1	2
Total other (loss) income					(40,220)	10,966	5,942	(14,341)	(77,752)	(37,650)	7,448
Total other (loss) income	22,821	(23,257)	(52,029)	(25,457)
Net (loss) income	29,742	(17,492)	(47,700)	(19,970)	(35,933)	17,365	14,933	(2,853)	(55,419)	(6,488)	54,372
Dividends on preferred stock	(2,297)	(2,297)	(2,297)	(2,297)	(2,297)	(2,297)	(2,297)	(2,297)	(9,189)	(9,189)	(8,173)
Net (loss) income to common stockholders	$ 27,445	$ (19,789)	$ (49,997)	$ (22,267)	$ (38,230)	$ 15,068	$ 12,636	$ (5,150)	$ (64,608)	$ (15,677)	$ 46,199
Basic (loss) income per common share	$ 0.28	$ (0.20)	$ (0.51)	$ (0.23)	$ (0.39)	$ 0.15	$ 0.13	$ (0.05)	$ (0.65)	$ (0.16)	$ 0.48
Diluted (loss) income per common share	$ 0.27	$ (0.20)	$ (0.51)	$ (0.23)	$ (0.39)	$ 0.15	$ 0.13	$ (0.05)	$ (0.65)	$ (0.16)	$ 0.47
Basic weighted average number of shares outstanding	98,823	98,739	98,635	98,537	98,444	98,353	98,271	98,185	98,739	98,314	96,764
Diluted weighted average number of shares outstanding	103,141	98,739	98,635	98,537	98,444	102,331	102,205	98,185	98,739	98,314	100,479