CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
U.S. Treasury securities, pledged assets	$ 0	$ 1,113,027	[1]
Agency mortgage-backed securities, pledged assets	66,110,869	63,897,873	[1]
Agency debentures, pledged assets	2,368,493	2,931,261	[1]
Receivable for investment advisory income, from affiliates	6,498	6,839	[1]
Preferred Stock, shares authorized	4,600,000
Common Stock, par value	$ 0.01	$ 0.01	[1]
Common Stock, shares authorized	1,956,937,500	1,956,937,500	[1]
Common Stock, shares issued	947,488,945	947,432,862	[1]
Common Stock, shares outstanding	947,488,945	947,432,862	[1]
Senior Secured mortgages of Consolidated VIE	1,640,206	1,583,969
Senior Securitized Mortgages
Senior Secured mortgages of Consolidated VIE	$ 398,100
7.875% Series A Cumulative Redeemable Preferred Stock
Preferred Stock, shares authorized	7,412,500	7,412,500	[1]
Preferred Stock, shares issued	7,412,500	7,412,500	[1]
Preferred Stock, shares outstanding	7,412,500	7,412,500	[1]
7.625% Series C Cumulative Redeemable Preferred Stock
Preferred Stock, shares authorized	12,650,000	12,650,000	[1]
Preferred Stock, shares issued	12,000,000	12,000,000	[1]
Preferred Stock, shares outstanding	12,000,000	12,000,000	[1]
7.50% Series D Cumulative Redeemable Preferred Stock
Preferred Stock, shares authorized	18,400,000	18,400,000	[1]
Preferred Stock, shares issued	18,400,000	18,400,000	[1]
Preferred Stock, shares outstanding	18,400,000	18,400,000	[1]

[1] Derived from the audited consolidated financial statements at December 31, 2013.