LOANS - Summary of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest income	$ 1,733,793	$ 1,330,513	$ 1,002,422
Net gains (losses) on disposal of investments and other	(62,705)	661,513	(47,944)
Net income (loss) attributable to Annaly	2,389,896	(891,163)	$ (2,162,865)
Residential mortgage loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest income	182,325	170,259
Net gains (losses) on disposal of investments and other	(37,212)	(38,372)
Net unrealized gains (losses) on instruments measured at fair value through earnings	19,545	37,693
Net income (loss) attributable to Annaly	$ 164,658	$ 169,580