SUMMARIZED QUARTERLY RESULTS (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 1,074,214	$ 919,299	$ 927,598	$ 866,186	$ 859,674	$ 816,596	$ 776,806	$ 879,487	$ 3,787,297	$ 3,332,563	$ 2,493,126
Interest expense	620,058	766,905	750,217	647,695	586,774	500,973	442,692	367,421	2,784,875	1,897,860	1,008,354
Net interest income	454,156	152,394	177,381	218,491	272,900	315,623	334,114	512,066	1,002,422	1,434,703	1,484,772
Total realized and unrealized gains (losses)	785,687	(875,406)	(1,909,482)	(1,011,926)	(2,502,035)	199,716	294,646	844,689	(3,011,127)	(1,162,984)	199,493
Total other income (loss)	42,656	35,074	28,181	30,502	52,377	(10,643)	34,170	34,023
Less: Total general and administrative expenses	73,351	66,138	78,408	83,737	77,073	126,509	63,781	62,510
Income (loss) before income taxes	1,209,148	(754,076)	(1,782,328)	(846,670)	(2,253,831)	378,187	599,149	1,328,268	(2,173,926)	51,773	1,575,998
Less: Income taxes	(594)	(6,907)	(5,915)	2,581	1,041	(7,242)	3,262	564	(10,835)	(2,375)	6,982
Net income (loss)	1,209,742	(747,169)	(1,776,413)	(849,251)	(2,254,872)	385,429	595,887	1,327,704	(2,163,091)	54,148	1,569,016
Less: Net income attributable to noncontrolling interests	68	(110)	(83)	(101)	17	(149)	(32)	(96)	(226)	(260)	(588)
Dividends on preferred stock	35,509	36,151	32,422	32,494	32,494	31,675	31,377	33,766	136,576	129,312	109,635
Net income (loss) available (related) to common stockholders	$ 1,174,165	$ (783,210)	$ (1,808,752)	$ (881,644)	$ (2,287,383)	$ 353,903	$ 564,542	$ 1,294,034	$ (2,299,441)	$ (74,904)	$ 1,459,969
Net income (loss) available (related) per share to common stockholders:
Basic (in dollars per share)	$ 0.82	$ (0.54)	$ (1.24)	$ (0.63)	$ (1.74)	$ 0.29	$ 0.49	$ 1.12	$ (1.60)	$ (0.06)	$ 1.37
Diluted (in dollars per share)	$ 0.82	$ (0.54)	$ (1.24)	$ (0.63)	$ (1.74)	$ 0.29	$ 0.49	$ 1.12	$ (1.60)	$ (0.06)	$ 1.37
Series I Preferred Stock
Class of Stock [Line Items]
Cumulative and undeclared dividends			$ 300