CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net interest income:
Interest income	$ 776,806	$ 537,426	$ 1,656,293	$ 1,125,153
Interest expense	442,692	222,281	810,113	420,706
Net interest income	334,114	315,145	846,180	704,447
Realized and unrealized gains (losses):
Net interest component of interest rate swaps	31,475	(96,470)	(16,685)	(200,626)
Realized gains (losses) on termination or maturity of interest rate swaps	0	(58)	834	(58)
Unrealized gains (losses) on interest rate swaps	343,475	(177,567)	1,320,760	(28,383)
Subtotal	374,950	(274,095)	1,304,909	(229,067)
Net gains (losses) on disposal of investments	(66,117)	(5,516)	(52,649)	(281)
Net gains (losses) on other derivatives	34,189	(14,423)	(12,956)	(14,104)
Net unrealized gains (losses) on instruments measured at fair value through earnings	(48,376)	16,240	(99,969)	39,923
Subtotal	(80,304)	(3,699)	(165,574)	25,538
Total realized and unrealized gains (losses)	294,646	(277,794)	1,139,335	(203,529)
Other income (loss):
Other income (loss)	34,170	30,865	68,193	62,511
Total other income (loss)	34,170	30,865	68,193	62,511
General and administrative expenses:
Compensation and management fee	45,579	38,938	90,108	78,200
Other general and administrative expenses	18,202	15,085	36,183	29,651
Total general and administrative expenses	63,781	54,023	126,291	107,851
Income (loss) before income taxes	599,149	14,193	1,927,417	455,578
Income taxes	3,262	(329)	3,826	648
Net income (loss)	595,887	14,522	1,923,591	454,930
Net income (loss) attributable to noncontrolling interest	(32)	(102)	(128)	(205)
Net income (loss) attributable to Annaly	595,919	14,624	1,923,719	455,135
Dividends on preferred stock	31,377	23,473	65,143	46,946
Net income (loss) available (related) to common stockholders	$ 564,542	$ (8,849)	$ 1,858,576	$ 408,189
Net income (loss) per share available (related) to common stockholders:
Basic (in dollars per share)	$ 0.49	$ (0.01)	$ 1.60	$ 0.40
Diluted (in dollars per share)	$ 0.49	$ (0.01)	$ 1.60	$ 0.40
Weighted average number of common shares outstanding:
Basic (in shares)	1,160,436,777	1,019,000,817	1,160,029,575	1,018,971,942
Diluted (in shares)	1,160,979,451	1,019,000,817	1,160,543,580	1,019,357,697
Dividends declared per share of common stock (in dollars per share)	$ 0.3	$ 0.3	$ 0.6	$ 0.60
Net income (loss)	$ 595,887	$ 14,522	$ 1,923,591	$ 454,930
Other comprehensive income (loss):
Unrealized gains (losses) on available-for-sale securities	(505,130)	261,964	(2,384,609)	202,349
Reclassification adjustment for net (gains) losses included in net income (loss)	70,763	13,360	76,182	32,777
Other comprehensive income (loss)	(434,367)	275,324	(2,308,427)	235,126
Comprehensive income (loss)	161,520	289,846	(384,836)	690,056
Comprehensive income (loss) attributable to noncontrolling interest	(32)	(102)	(128)	(205)
Comprehensive income (loss) attributable to Annaly	161,552	289,948	(384,708)	690,261
Comprehensive income (loss) attributable to common stockholders	$ 130,175	$ 266,475	$ (449,851)	$ 643,315