NET INCOME (LOSS) PER COMMON SHARE - Schedule of Net Income (Loss) per Share Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Net income (loss)	$ 2,023,894	$ 1,751,134
Net income (loss) attributable to noncontrolling interests	1,639	321
Net income (loss) attributable to Annaly	2,022,255	1,750,813
Dividends on preferred stock	26,883	26,883
Net income (loss) available (related) to common stockholders	$ 1,995,372	$ 1,723,930
Weighted average shares of common stock outstanding-basic (in shares)	1,461,363,637	1,399,210,925
Add: Effect of stock awards, if dilutive (in shares)	1,088,328	789,802
Weighted average shares of common stock outstanding-diluted (in shares)	1,462,451,965	1,400,000,727
Net income (loss) per share available (related) to common share
Basic (in dollars per share)	$ 1.37	$ 1.23
Diluted (in dollars per share)	$ 1.36	$ 1.23