Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating activities:
Net income	$ 128,542	$ 118,236
Noncash items:
Amortization of investment premiums	67,346	48,023
Depreciation and other amortization	142	159
Equity-based compensation costs	1,661	1,352
Change in measureable hedge ineffectiveness related to interest rate swap agreements	(464)	575
Impairment charge related to real estate held for sale		470
Gain on sales of real estate held for sale	(273)	(50)
Net change in receivables, other assets, accounts payable and accrued expenses	(3,350)	(753)
Net cash provided by operating activities	193,604	168,012
Investing activities:
Purchases of residential mortgage investments	(3,936,151)	(5,263,254)
Purchased interest receivable related to purchases of residential mortgage investments	(6,390)	(10,999)
Proceeds from sales of real estate held for sale	2,010	1,029
Principal collections on residential mortgage investments	1,918,542	1,517,116
Net cash used in investing activities	(2,021,989)	(3,756,108)
Financing activities:
Proceeds from repurchase arrangements and similar borrowings	100,706,383	66,614,532
Principal payments on repurchase arrangements and similar borrowings	(98,808,335)	(63,319,411)
Increase in cash collateral receivable from interest rate swap counterparties	(9,232)	(21,839)
Decrease in cash collateral payable to interest rate swap counterparties		(9,024)
Capital stock transactions	145,930	197,653
Dividends paid	(132,337)	(112,238)
Net cash provided by financing activities	1,902,409	3,349,673
Net change in cash and cash equivalents	74,024	(238,423)
Cash and cash equivalents at beginning of period	426,717	359,590
Cash and cash equivalents at end of period	$ 500,741	$ 121,167