CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash Flows From Operating Activities:
Net income	$ 77,351	$ 84,713
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of MBS and U.S. Treasury securities	(1,633)	(2,953)
Other-than-temporary impairment charges		920
Accretion of purchase discounts on MBS	(12,058)	(9,418)
Amortization of purchase premiums on MBS	14,793	10,782
Depreciation and amortization on fixed assets and other assets	1,097	427
Equity-based compensation expense	885	1,101
Unrealized gains and other on Linked Transactions	(1,136)	(6,245)
Decrease in interest receivable	1,891	244
(Increase)/decrease in prepaid and other assets	(4,088)	1,844
Decrease in accrued expenses and other liabilities, and excise tax and interest	(2,699)	(3,886)
(Decrease)/increase in accrued interest payable on financial instruments	(3,237)	2,404
Net cash provided by operating activities	71,166	79,933
Cash Flows From Investing Activities:
Principal payments on MBS	711,901	558,516
Proceeds from sale of MBS and U.S. Treasury securities	206,203	71,103
Purchases of MBS	(569,006)	(737,950)
Additions to leasehold improvements, furniture and fixtures	(54)	(130)
Net cash provided by/(used in) investing activities	349,044	(108,461)
Cash Flows From Financing Activities:
Principal payments on repurchase agreements	(18,024,857)	(14,744,454)
Proceeds from borrowings under repurchase agreements	18,175,212	14,840,227
Proceeds from issuance of securitized debt		186,691
Principal payments on securitized debt	(104,802)	(94,789)
Payments made on obligation to return securities obtained as collateral	(200,050)
Payments made for resecuritization related costs		(1,763)
Cash disbursements on financial instruments underlying Linked Transactions	(57,977)	(299,173)
Cash received from financial instruments underlying Linked Transactions	59,245	218,269
Payments made for margin calls on repurchase agreements and interest rate swaps ("Swaps")		(1,590)
Proceeds from reverse margin calls on repurchase agreements and Swaps		4,090
Proceeds from issuances of common stock	7,278	451
Dividends paid on preferred stock	(2,040)	(2,040)
Dividends paid on common stock and DERs	(71,942)	(96,792)
Net cash (used in)/provided by financing activities	(219,933)	9,127
Net increase/(decrease) in cash and cash equivalents	200,277	(19,401)
Cash and cash equivalents at beginning of period	401,293	394,022
Cash and cash equivalents at end of period	601,570	374,621
Non-cash Investing and Financing Activities:
MBS recorded upon de-linking of Linked Transactions		122,826
Net increase in securities obtained as collateral/obligation to return securities obtained as collateral	200,099	197,339
Dividends and DERs declared and unpaid	$ 259,607	$ 86,778