CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net interest income
Interest income	$ 866,186,000	$ 879,487,000
Interest expense	647,695,000	367,421,000
Net interest income	218,491,000	512,066,000
Realized and unrealized gains (losses)
Net interest component of interest rate swaps	134,035,000	(48,160,000)
Realized gains (losses) on termination or maturity of interest rate swaps	(588,256,000)	834,000
Unrealized gains (losses) on interest rate swaps	(390,556,000)	977,285,000
Subtotal	(844,777,000)	929,959,000
Net gains (losses) on disposal of investments	(93,916,000)	13,468,000
Net gains (losses) on other derivatives	(115,159,000)	(47,145,000)
Net unrealized gains (losses) on instruments measured at fair value through earnings	47,629,000	(51,593,000)
Loan loss provision	(5,703,000)	0
Subtotal	(167,149,000)	(85,270,000)
Total realized and unrealized gains (losses)	(1,011,926,000)	844,689,000
Other income (loss)	30,502,000	34,023,000
General and administrative expenses
Compensation and management fee	44,833,000	44,529,000
Other general and administrative expenses	38,904,000	17,981,000
Total general and administrative expenses	83,737,000	62,510,000
Income (loss) before income taxes	(846,670,000)	1,328,268,000
Income taxes	2,581,000	564,000
Net income (loss)	(849,251,000)	1,327,704,000
Net income (loss) attributable to noncontrolling interests	(101,000)	(96,000)
Net income (loss) attributable to Annaly	(849,150,000)	1,327,800,000
Dividends on preferred stock	32,494,000	33,766,000
Net income (loss) available (related) to common stockholders	$ (881,644,000)	$ 1,294,034,000
Net income (loss) per share available (related) to common stockholders
Basic (in dollars per share)	$ (0.63)	$ 1.12
Diluted (in dollars per share)	$ (0.63)	$ 1.12
Weighted average number of common shares outstanding
Basic (in shares)	1,398,614,205	1,159,617,848
Diluted (in shares)	1,398,614,205	1,160,103,185
Net income (loss)	$ (849,251,000)	$ 1,327,704,000
Other comprehensive income (loss)
Unrealized gains (losses) on available-for-sale securities	1,599,398,000	(1,879,479,000)
Reclassification adjustment for net (gains) losses included in net income (loss)	61,091,000	5,419,000
Other comprehensive income (loss)	1,660,489,000	(1,874,060,000)
Comprehensive income (loss)	811,238,000	(546,356,000)
Comprehensive income (loss) attributable to noncontrolling interests	(101,000)	(96,000)
Comprehensive income (loss) attributable to Annaly	811,339,000	(546,260,000)
Dividends on preferred stock	32,494,000	33,766,000
Comprehensive income (loss) attributable to common stockholders	$ 778,845,000	$ (580,026,000)