CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Net interest income:
Interest income		$ 879,487	$ 587,727
Interest expense		367,421	198,425
Net interest income		512,066	389,302
Realized and unrealized gains (losses):
Realized gains (losses) on interest rate swaps	[1]	(48,160)	(104,156)
Realized gains (losses) on termination or maturity of interest rate swaps		834	0
Unrealized gains (losses) on interest rate swaps		977,285	149,184
Subtotal		929,959	45,028
Net gains (losses) on disposal of investments		13,468	5,235
Net gains (losses) on trading assets		(47,145)	319
Net unrealized gains (losses) on investments measured at fair value through earnings		(51,593)	23,683
Subtotal		(85,270)	29,237
Total realized and unrealized gains (losses)		844,689	74,265
Other income (loss):
Other income (loss)		34,023	31,646
Total other income (loss)		34,023	31,646
General and administrative expenses:
Compensation and management fee		44,529	39,262
Other general and administrative expenses		17,981	14,566
Total general and administrative expenses		62,510	53,828
Income (loss) before income taxes		1,328,268	441,385
Income taxes		564	977
Net income (loss)		1,327,704	440,408
Net income (loss) attributable to noncontrolling interest		(96)	(103)
Net income (loss) attributable to Annaly		1,327,800	440,511
Dividends on preferred stock		33,766	23,473
Net income (loss) available (related) to common stockholders		$ 1,294,034	$ 417,038
Net income (loss) per share available (related) to common stockholders:
Basic (in dollars per share)		$ 1.12	$ 0.41
Diluted (in dollars per share)		$ 1.12	$ 0.41
Weighted average number of common shares outstanding:
Basic (in shares)		1,159,617,848	1,018,942,746
Diluted (in shares)		1,160,103,185	1,019,307,379
Dividends declared per share of common stock (in dollars per share)		$ 0.3	$ 0.30
Net income (loss)		$ 1,327,704	$ 440,408
Other comprehensive income (loss):
Unrealized gains (losses) on available-for-sale securities		(1,879,479)	(59,615)
Reclassification adjustment for net (gains) losses included in net income (loss)		5,419	19,417
Other comprehensive income (loss)		(1,874,060)	(40,198)
Comprehensive income (loss)		(546,356)	400,210
Comprehensive income (loss) attributable to noncontrolling interest		(96)	(103)
Comprehensive income (loss) attributable to Annaly		(546,260)	400,313
Comprehensive income (loss) attributable to common stockholders		$ (580,026)	$ 376,840

[1] Consists of interest expense on interest rate swaps.