Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets [Abstract]
Cash	$ 382,796	$ 295,602
Cash collateral posted to counterparties	16,639	14,758
Mortgage-backed securities (including pledged of $2,677,652 and $2,467,859, respectively), at fair value	2,858,166	2,596,255
Mortgage loans held for investment, at fair value	4,717	6,264
Receivable for sales pending settlement	806	150,432
Derivative assets	70,098	11,342
Accrued interest receivable	13,752	14,388
Other assets, net	7,136	6,394
Total assets	3,354,110	3,095,435
Liabilities:
Repurchase agreements	2,527,065	2,437,163
Payable for purchases pending settlement	5,429	5
Derivative liabilities	12,584	1,634
Derivative Asset, Collateral, Obligation to Return Cash, Offset	22,632	7,681
Accrued interest payable	639	1,410
Accrued dividends payable	6,350	5,814
Other liabilities	5,900	8,275
Total liabilities	2,580,599	2,461,982
Stockholders' Equity Attributable to Parent [Abstract]
Preferred stock, par value $0.01 per share; 50,000,000 shares authorized; 4,460,000 and 7,248,330 shares issued and outstanding, respectively ($111,500 and $181,208 aggregate liquidation preference, respectively)	107,843	174,564
Common stock, par value $0.01 per share, 90,000,000 shares authorized; 35,935,306 and 23,697,970 shares issued and outstanding, respectively	359	237
Additional paid-in capital	1,094,296	869,495
Accumulated other comprehensive income	20,236	80,261
Accumulated deficit	(449,223)	(491,104)
Total shareholders’ equity	773,511	633,453
Total liabilities and shareholders’ equity	$ 3,354,110	$ 3,095,435