CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash Flows From Operating Activities:
Net income	$ 237,620	$ 245,850
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of MBS	(7,232)	(4,196)
Other-than-temporary impairment charges	1,200	6,383
Accretion of purchase discounts on MBS	(28,173)	(33,159)
Amortization of purchase premiums on MBS	38,175	26,779
Increase in interest receivable	(1,998)	(6,125)
Depreciation and amortization on real estate and other assets	2,471	2,263
Unrealized (gains)/losses and other on Linked Transactions	(8,851)	4,831
Increase in prepaid and other assets	(10,342)	(47)
Increase in accrued expenses and other liabilities	344	37
Increase/(decrease) in accrued interest payable	5,005	(529)
Equity-based compensation expense	4,374	2,983
Net cash provided by operating activities	232,593	245,070
Cash Flows From Investing Activities:
Principal payments on MBS	1,977,366	1,688,520
Proceeds from sale of MBS	137,079	76,495
Purchases of MBS	(2,896,359)	(4,430,941)
Additions to leasehold improvements, furniture, fixtures and real estate investment	(367)	(2,004)
Net cash used in investing activities	(782,281)	(2,667,930)
Cash Flows From Financing Activities:
Principal payments on repurchase agreements	(48,911,503)	(43,843,055)
Proceeds from borrowings under repurchase agreements	49,930,670	45,821,751
Proceeds from issuance of securitized debt	186,691	963,255
Principal payments on securitized debt	(312,740)	(225,782)
Payments made for resecuritization related costs	(1,814)	(6,981)
Proceeds from issuance of Senior Notes	100,000
Payments made for Senior Notes related costs	(3,415)
Cash disbursements on financial instruments underlying Linked Transactions	(513,418)	(2,051,908)
Cash received from financial instruments underlying Linked Transactions	390,363	1,464,965
Payments made for margin calls on repurchase agreements and interest rate swap agreements ("Swaps")	(2,390)	(8,460)
Proceeds from reverse margin calls on repurchase agreements and Swaps	10,890	25,914
Payment made to purchase interest rate swaption ("Swaption")		(915)
Proceeds from issuances of common stock	4,398	605,765
Dividends paid on preferred stock	(6,120)	(6,120)
Dividends paid on common stock and DERs	(265,504)	(239,786)
Net cash provided by financing activities	606,108	2,498,643
Net increase in cash and cash equivalents	56,420	75,783
Cash and cash equivalents at beginning of period	394,022	345,243
Cash and cash equivalents at end of period	450,442	421,026
Non-cash Investing and Financing Activities:
MBS recorded upon de-linking of Linked Transactions	174,940	744,231
Repurchase agreements recorded upon de-linking of Linked Transactions		46,698
Securities obtained as collateral	203,303
Dividends and DERs declared and unpaid	$ 76,051	$ 90,200