CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Operating activities:
Net income	$ 33,957	$ 38,391
Noncash items:
Amortization of investment premiums	25,078	22,288
Amortization of equity-based awards	724	718
Other depreciation and amortization	33	37
Change in measurable hedge ineffectiveness related to interest rate swap agreements designated as cash flow hedges	185	0
Net change in receivables, other assets, accounts payable and accrued expenses	(1,131)	(37)
Net cash provided by operating activities	58,846	61,397
Investing activities:
Purchases of residential mortgage investments	(959,548)	(669,003)
Interest receivable acquired with the purchase of residential mortgage investments	(1,534)	(1,121)
Principal collections on residential mortgage investments, including changes in mortgage securities principal remittance receivable	703,688	617,074
Net cash used in investing activities	(257,394)	(53,050)
Financing activities:
Proceeds from repurchase arrangements and similar borrowings	29,887,321	31,981,126
Principal payments on repurchase arrangements and similar borrowings	(29,755,657)	(31,873,771)
Increase in cash collateral receivable from interest rate swap Counterparties	(8,530)	(10,494)
Proceeds from issuance of preferred shares	10,651	1,336
Other capital stock transactions	(429)	(512)
Dividends paid	(36,719)	(33,095)
Net cash provided by financing activities	96,637	64,590
Net change in cash and cash equivalents	(101,911)	72,937
Cash and cash equivalents at beginning of period	307,526	413,356
Cash and cash equivalents at end of period	$ 205,615	$ 486,293