NET INCOME (LOSS) PER COMMON SHARE - Schedule of Net Income (Loss) per Share Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Net income (loss)	$ 863,317	$ (294,848)	$ 2,887,211	$ 1,456,286
Net income (loss) attributable to noncontrolling interests	(3,379)	794	(1,740)	1,115
Net income (loss) attributable to Annaly	866,696	(295,642)	2,888,951	1,455,171
Dividends on preferred stock	26,883	26,883	53,766	53,766
Net income (loss) available (related) to common stockholders	$ 839,813	$ (322,525)	$ 2,835,185	$ 1,401,405
Weighted average shares of common stock outstanding-basic (in shares)	1,522,436,766	1,410,239,138	1,492,068,912	1,404,755,496
Add: Effect of stock awards, if dilutive (in shares)	1,158,234	0	1,185,978	1,008,776
Weighted average shares of common stock outstanding-diluted (in shares)	1,523,595,000	1,410,239,138	1,493,254,890	1,405,764,272
Net income (loss) per share available (related) to common share
Basic (in dollars per share)	$ 0.55	$ (0.23)	$ 1.90	$ 1.00
Diluted (in dollars per share)	$ 0.55	$ (0.23)	$ 1.90	$ 1.00