CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash Flows From Operating Activities:
Net income	$ 76,188	$ 77,351
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of MBS and U.S. Treasury securities	(3,571)	(1,633)
Accretion of purchase discounts on MBS	(27,434)	(12,058)
Amortization of purchase premiums on MBS	10,215	14,793
Depreciation and amortization on fixed assets and other assets	327	1,097
Equity-based compensation expense	1,484	885
Unrealized gains on derivative instruments	(2,076)	(1,136)
(Increase)/decrease in interest receivable	(863)	1,891
Increase in prepaid and other assets	(9,644)	(4,088)
Decrease in accrued expenses and other liabilities, and excise tax and interest	(3,745)	(2,699)
Increase/(decrease) in accrued interest payable on financial instruments	7,384	(3,237)
Net cash provided by operating activities	48,265	71,166
Cash Flows From Investing Activities:
Principal payments on MBS	438,149	711,901
Proceeds from sale of MBS and U.S. Treasury securities	15,501	206,203
Purchases of MBS	(888,106)	(569,006)
Additions to leasehold improvements, furniture and fixtures	(85)	(54)
Net cash (used in)/provided by investing activities	(434,541)	349,044
Cash Flows From Financing Activities:
Principal payments on repurchase agreements	(20,203,589)	(18,024,857)
Proceeds from borrowings under repurchase agreements	20,470,421	18,175,212
Principal payments on securitized debt	(73,262)	(104,802)
Payments made on obligation to return securities obtained as collateral	0	(200,050)
Cash disbursements on financial instruments underlying Linked Transactions	(374,073)	(57,977)
Cash received from financial instruments underlying Linked Transactions	344,504	59,245
Payments made for margin calls on repurchase agreements and Swaps	(29,000)	0
Proceeds from reverse margin calls on repurchase agreements and Swaps	30,000	0
Proceeds from issuances of common stock	7,616	7,278
Dividends paid on preferred stock	(3,750)	(2,040)
Dividends paid on common stock and DERs	(73,289)	(71,942)
Net cash provided by/(used in) financing activities	95,578	(219,933)
Net (decrease)/increase in cash and cash equivalents	(290,698)	200,277
Cash and cash equivalents at beginning of period	565,370	401,293
Cash and cash equivalents at end of period	274,672	601,570
Non-cash Investing and Financing Activities:
Net increase in securities obtained as collateral/obligation to return securities obtained as collateral	47,768	200,099
Dividends and DERs declared and unpaid	$ 73,875	$ 259,607