CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net interest income
Interest income		$ 927,598,000	$ 776,806,000	$ 1,793,784,000	$ 1,656,293,000
Interest expense		750,217,000	442,692,000	1,397,912,000	810,113,000
Net interest income		177,381,000	334,114,000	395,872,000	846,180,000
Realized and unrealized gains (losses)
Net interest component of interest rate swaps		83,653,000	31,475,000	217,688,000	(16,685,000)
Realized gains (losses) on termination or maturity of interest rate swaps		(167,491,000)	0	(755,747,000)	834,000
Unrealized gains (losses) on interest rate swaps		(1,276,019,000)	343,475,000	(1,666,575,000)	1,320,760,000
Subtotal		(1,359,857,000)	374,950,000	(2,204,634,000)	1,304,909,000
Net gains (losses) on disposal of investments		(38,333,000)	(66,117,000)	(132,249,000)	(52,649,000)
Net gains (losses) on other derivatives		(506,411,000)	34,189,000	(621,570,000)	(12,956,000)
Net unrealized gains (losses) on instruments measured at fair value through earnings		(4,881,000)	(48,376,000)	42,748,000	(99,969,000)
Loan loss provision		0	0	(5,703,000)	0
Subtotal		(549,625,000)	(80,304,000)	(716,774,000)	(165,574,000)
Total realized and unrealized gains (losses)		(1,909,482,000)	294,646,000	(2,921,408,000)	1,139,335,000
Other income (loss)		28,181,000	34,170,000	58,683,000	68,193,000
General and administrative expenses
Compensation and management fee		44,231,000	45,579,000	89,064,000	90,108,000
Other general and administrative expenses		34,177,000	18,202,000	73,081,000	36,183,000
Total general and administrative expenses		78,408,000	63,781,000	162,145,000	126,291,000
Income (loss) before income taxes		(1,782,328,000)	599,149,000	(2,628,998,000)	1,927,417,000
Income taxes		(5,915,000)	3,262,000	(3,334,000)	3,826,000
Net income (loss)		(1,776,413,000)	595,887,000	(2,625,664,000)	1,923,591,000
Net income (loss) attributable to noncontrolling interests		(83,000)	(32,000)	(184,000)	(128,000)
Net income (loss) attributable to Annaly		(1,776,330,000)	595,919,000	(2,625,480,000)	1,923,719,000
Dividends on preferred stock (1)	[1]	32,422,000	31,377,000	64,916,000	65,143,000
Net income (loss) available (related) to common stockholders		$ (1,808,752,000)	$ 564,542,000	$ (2,690,396,000)	$ 1,858,576,000
Net income (loss) per share available (related) to common stockholders
Basic (in dollars per share)		$ (1.24)	$ 0.49	$ (1.88)	$ 1.60
Diluted (in dollars per share)		$ (1.24)	$ 0.49	$ (1.88)	$ 1.60
Weighted average number of common shares outstanding
Basic (in shares)		1,456,038,736	1,160,436,777	1,427,485,102	1,160,029,575
Diluted (in shares)		1,456,038,736	1,160,979,451	1,427,485,102	1,160,543,580
Net income (loss)		$ (1,776,413,000)	$ 595,887,000	$ (2,625,664,000)	$ 1,923,591,000
Other comprehensive income (loss)
Unrealized gains (losses) on available-for-sale securities		1,654,783,000	(505,130,000)	3,254,181,000	(2,384,609,000)
Reclassification adjustment for net (gains) losses included in net income (loss)		29,596,000	70,763,000	90,687,000	76,182,000
Other comprehensive income (loss)		1,684,379,000	(434,367,000)	3,344,868,000	(2,308,427,000)
Comprehensive income (loss)		(92,034,000)	161,520,000	719,204,000	(384,836,000)
Comprehensive income (loss) attributable to noncontrolling interests		(83,000)	(32,000)	(184,000)	(128,000)
Comprehensive income (loss) attributable to Annaly		(91,951,000)	161,552,000	719,388,000	(384,708,000)
Dividends on preferred stock (1)	[1]	32,422,000	31,377,000	64,916,000	65,143,000
Comprehensive income (loss) attributable to common stockholders		(124,373,000)	$ 130,175,000	654,472,000	$ (449,851,000)
Cumulative and undeclared dividends		$ 300,000		$ 300,000

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