CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
U.S. Treasury Securities, pledged assets	$ 1,645,930	$ 752,076	[1]
Agency mortgage-backed securities , pledged assets	98,719,355	107,466,084	[1]
Agency debentures, pledged assets	2,707,919	981,727	[1]
Receivable for advisory and service fees, from affiliates	9,244	14,077	[1]
Intangible for customer relationships, accumulated amortization	$ 6,037	$ 5,779	[1]
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	947,293,099	947,213,204	[1]
Common Stock, shares outstanding	947,293,099	947,213,204	[1]
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, 2012.