CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net interest income
Interest income	$ 2,229,625	$ 3,787,297	$ 3,332,563
Interest expense	899,112	2,784,875	1,897,860
Net interest income	1,330,513	1,002,422	1,434,703
Realized and unrealized gains (losses)
Net interest component of interest rate swaps	(207,877)	351,375	100,553
Realized gains (losses) on termination or maturity of interest rate swaps	(1,917,628)	(1,442,964)	1,409
Unrealized gains (losses) on interest rate swaps	(904,532)	(1,210,276)	424,081
Subtotal	(3,030,037)	(2,301,865)	526,043
Net gains (losses) on disposal of investments	661,513	(47,944)	(1,124,448)
Net gains (losses) on other derivatives	756,305	(680,770)	(403,001)
Net unrealized gains (losses) on instruments measured at fair value through earnings	(303,024)	36,021	(158,082)
Loan loss provision	(147,581)	(16,569)	(3,496)
Subtotal	967,213	(709,262)	(1,689,027)
Total realized and unrealized gains (losses)	(2,062,824)	(3,011,127)	(1,162,984)
Other income (loss)	53,314	136,413	109,927
General and administrative expenses
Compensation and management fee	131,685	170,628	179,841
Other general and administrative expenses	107,513	131,006	150,032
Total general and administrative expenses	239,198	301,634	329,873
Income (loss) before income taxes	(918,195)	(2,173,926)	51,773
Income taxes	(28,423)	(10,835)	(2,375)
Net income (loss)	(889,772)	(2,163,091)	54,148
Net income (loss) attributable to noncontrolling interests	1,391	(226)	(260)
Net income (loss) attributable to Annaly	(891,163)	(2,162,865)	54,408
Dividends on preferred stock	142,036	136,576	129,312
Net income (loss) available (related) to common stockholders	$ (1,033,199)	$ (2,299,441)	$ (74,904)
Net income (loss) per share available (related) to common stockholders
Basic (in dollars per share)	$ (0.73)	$ (1.60)	$ (0.06)
Diluted (in dollars per share)	$ (0.73)	$ (1.60)	$ (0.06)
Weighted average number of common shares outstanding
Basic (in shares)	1,414,659,439	1,434,912,682	1,209,601,809
Diluted (in shares)	1,414,659,439	1,434,912,682	1,209,601,809
Other comprehensive income (loss)
Net income (loss)	$ (889,772)	$ (2,163,091)	$ 54,148
Unrealized gains (losses) on available-for-sale securities	2,012,878	4,135,862	(2,004,166)
Reclassification adjustment for net (gains) losses included in net income (loss)	(776,734)	(17,806)	1,150,321
Other comprehensive income (loss)	1,236,144	4,118,056	(853,845)
Comprehensive income (loss)	346,372	1,954,965	(799,697)
Comprehensive income (loss) attributable to noncontrolling interests	1,391	(226)	(260)
Comprehensive income (loss) attributable to Annaly	344,981	1,955,191	(799,437)
Comprehensive income (loss) attributable to common stockholders	$ 202,945	$ 1,818,615	$ (928,749)