Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Interest Paid	$ 409	$ 249	$ 66
Operating activities:
Net income (loss)	1,277	770	288
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of agency securities premiums and discounts, net	667	361	99
Amortization of accumulated other comprehensive loss on interest rate swaps de-designated as qualifying hedges	205	54	0
Gain on sale of agency securities, net	(1,196)	(473)	(92)
Loss (gain) on derivative instruments and other securities, net	1,353	447	(38)
Increase in other assets	(76)	(121)	(28)
Increase in accounts payable and other accrued liabilities	86	32	4
Accretion of discounts on debt of consolidated variable interest entities	5	0	0
Net cash provided by operating activities	2,321	1,070	233
Investing activities:
Purchases of agency securities	(104,703)	(81,484)	(22,645)
Proceeds from sale of agency securities	65,249	37,868	12,062
Principal collections on agency securities	9,576	4,633	1,581
Purchases of U.S. Treasury securities	(2,444)	(5,163)	(1,305)
Proceeds from sale of U.S. Treasury securities	2,545	5,096	1,300
Proceeds from U.S. Treasury securities sold prior to purchase	36,467	17,301	0
Purchase of U.S. Treasury securities sold prior to purchase	(25,752)	(16,781)	0
Proceeds from reverse repurchase agreements	91,741	37,349	0
Payments made on reverse repurchase agreements	(102,796)	(37,865)	(248)
Net (payments) receipts on other derivative instruments not designated as qualifying hedges	(1,001)	(266)	256
Decrease in restricted cash	(63)	(260)	(57)
Net cash used in investing activities	(31,181)	(39,572)	(9,056)
Financing activities:
Proceeds from repurchase arrangements, net	404,853	339,046	83,819
Payments made on repurchase agreements	(378,056)	(303,044)	(75,981)
Proceeds from other debt	1,000	0	81
Repayments on other debt	(150)	(19)	(8)
Proceeds from Issuance of Preferred Stock and Preference Stock	167	0	0
Net proceeds from common stock issuances	3,601	4,377	1,055
Payments made on common stock repurchases	77	0	0
Cash dividends paid	(1,415)	(664)	(173)
Net cash provided by financing activities	29,923	39,696	8,793
Net change in cash and cash equivalents	1,063	1,194	(30)
Cash and cash equivalents at beginning of period	1,367	173	203
Cash and cash equivalents at end of period	2,430	1,367	173
Taxes Paid	$ 10	$ 0	$ 0