CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total		Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit		Accumulated Deficit Impact of adopting CECL	Accumulated Deficit CECL provision, adjusted balance	Total Stockholders’ Equity	Noncontrolling Interest
Beginning of period at Dec. 31, 2018				$ 1,778,168	$ 13,138	$ 18,794,331	$ (1,979,865)	$ (4,493,660)		$ 0	$ (4,493,660)		$ 5,689
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance				428,324	1,422	1,397,484
Redemption				(224,466)		(5,534)
Buyback of common stock					(182)	(155,122)
Stock-based award activity					0	2,018
Direct purchase and dividend reinvestment		$ 1,795			2	1,793
Unrealized gains (losses) on available-for-sale securities		4,289,054					4,289,054
Reclassification adjustment for net (gains) losses included in net income (loss)		4,626					4,626
Net income (loss) attributable to Annaly		(3,372,539)						(3,372,539)
Dividends declared on preferred stock	[1]							(101,067)
Dividends and dividend equivalents declared on common stock and share-based awards		(1,158,629)						(1,158,629)	[1]
Net income (loss) attributable to noncontrolling interests		294											(294)
Equity contributions from (distributions to) noncontrolling interest													(987)
End of period at Sep. 30, 2019		15,223,704		1,982,026	14,380	20,034,970	2,313,815	(9,125,895)				$ 15,219,296	4,408
Beginning of period at Jun. 30, 2019				2,110,346	14,562	20,195,419	1,365,003	(7,982,649)		0	(7,982,649)		4,726
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance				41,146	0	0
Redemption				(169,466)		(5,534)
Buyback of common stock					(182)	(155,122)
Stock-based award activity					0	207
Direct purchase and dividend reinvestment					0	0
Unrealized gains (losses) on available-for-sale securities		1,034,873					1,034,873
Reclassification adjustment for net (gains) losses included in net income (loss)		(86,061)					(86,061)
Net income (loss) attributable to Annaly		(747,059)						(747,059)
Dividends declared on preferred stock	[1]							(36,451)
Dividends and dividend equivalents declared on common stock and share-based awards		(359,736)						(359,736)	[1]
Net income (loss) attributable to noncontrolling interests		110											(110)
Equity contributions from (distributions to) noncontrolling interest													(208)
End of period at Sep. 30, 2019		15,223,704		1,982,026	14,380	20,034,970	2,313,815	(9,125,895)				15,219,296	4,408
Beginning of period at Dec. 31, 2019		15,796,344	[2]	1,982,026	14,301	19,966,923	2,138,191	(8,309,424)		(39,641)	(8,349,065)		4,327
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance				0	0	(93)
Redemption				0		0
Buyback of common stock					(277)	(174,799)
Stock-based award activity					3	4,928
Direct purchase and dividend reinvestment		1,075			2	1,073
Unrealized gains (losses) on available-for-sale securities		2,220,271					2,220,271
Reclassification adjustment for net (gains) losses included in net income (loss)		(769,406)					(769,406)
Net income (loss) attributable to Annaly		(1,768,379)						(1,768,379)
Dividends declared on preferred stock	[1]							(106,527)
Dividends and dividend equivalents declared on common stock and share-based awards		(976,966)						(976,966)	[1]
Net income (loss) attributable to noncontrolling interests		28											(28)
Equity contributions from (distributions to) noncontrolling interest													8,167
End of period at Sep. 30, 2020		14,194,672		1,982,026	14,029	19,798,032	3,589,056	(11,200,937)				14,182,206	12,466
Beginning of period at Jun. 30, 2020				1,982,026	14,077	19,827,216	3,842,074	(11,871,927)		$ 0	$ (11,871,927)		4,137
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance				0	0	0
Redemption				0		0
Buyback of common stock					(49)	(31,363)
Stock-based award activity					0	1,510
Direct purchase and dividend reinvestment					1	669
Unrealized gains (losses) on available-for-sale securities		(140,671)					(140,671)
Reclassification adjustment for net (gains) losses included in net income (loss)		(112,347)					(112,347)
Net income (loss) attributable to Annaly		1,015,674						1,015,674
Dividends declared on preferred stock	[1]							(35,509)
Dividends and dividend equivalents declared on common stock and share-based awards		(309,175)						(309,175)	[1]
Net income (loss) attributable to noncontrolling interests		126											(126)
Equity contributions from (distributions to) noncontrolling interest													8,455
End of period at Sep. 30, 2020		$ 14,194,672		$ 1,982,026	$ 14,029	$ 19,798,032	$ 3,589,056	$ (11,200,937)				$ 14,182,206	$ 12,466

[1] The three months ended September 30, 2019 exclude cumulative and undeclared dividends of $0.3 million on the Company's Series I Preferred Stock as of June 30, 2019.

[2] Derived from the audited consolidated financial statements at December 31, 2019.