Schedule of Net Income (Loss) Per Share Reconciliation (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Net Income Per Common Share:
Net income (loss) attributable to Annaly	$ (476,409)	$ (203,351)
Less: Preferred stock dividends	17,992	17,992
Net income (loss) per share available (related) to common stockholders, prior to adjustment for dilutive potential common shares, if necessary	(494,401)	(221,343)
Add: Interest on Convertible Senior Notes, if dilutive	0	0
Net income (loss) available to common stockholders, as adjusted	(494,401)	(221,343)
Weighted average shares of common stock outstanding-basic	947,669,831	947,458,813
Add: Effect of stock awards and Convertible Senior Notes, if dilutive	0	0
Weighted average shares of common stock outstanding-diluted	947,669,831	947,458,813
Net income (loss) per share available (related) to common share:
Basic	$ (0.52)	$ (0.23)
Diluted	$ (0.52)	$ (0.23)
Parent
Net Income Per Common Share:
Net income (loss) attributable to Annaly	$ (476,409)	$ (203,351)