CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 79,589	$ 82,873	$ 108,325
Noncash items:
Amortization of investment premiums	128,769	130,084	121,190
Amortization of equity-based awards	1,404	1,440	2,132
Other depreciation and amortization	111	124	109
Change in measureable hedge ineffectiveness related to interest rate swap agreements designated as cash flow hedges	36	(47)	(162)
Net change in receivables, other assets, accounts payable and accrued expenses	2,167	646	12,651
Net cash provided by operating activities	212,076	215,120	244,245
Investing activities:
Purchases of residential mortgage investments	(4,224,515)	(3,185,113)	(3,887,051)
Interest receivable acquired with the purchase of residential mortgage investments	(6,739)	(4,361)	(5,494)
Principal collections on residential mortgage investments, including changes in mortgage securities principal remittance receivable	3,914,865	3,817,351	3,419,867
Redemptions (purchases) of lending counterparty investments		60,000	(60,002)
Net cash (used in) provided by investing activities	(316,389)	687,877	(532,680)
Financing activities:
Proceeds from repurchase arrangements and similar borrowings	177,916,331	127,822,442	111,006,967
Principal payments on repurchase arrangements and similar borrowings	(177,730,614)	(125,760,487)	(113,730,416)
Proceeds from other secured borrowings		1,175,000	5,425,000
Principal payments on other secured borrowings		(4,050,000)	(2,550,000)
(Increase) decrease in cash collateral receivable from interest rate swap counterparties	(12,846)	20,533	2,946
Net proceeds from interest rate swap settlements	27,793
Proceeds from issuance of preferred shares	52,051	1,898	13,266
Common stock repurchases	3,460
Other capital stock transactions	(261)	(57)	(429)
Dividends paid	(97,506)	(109,779)	(132,240)
Net cash provided by (used in) financing activities	151,488	(900,450)	35,094
Net change in cash and cash equivalents	47,175	2,547	(253,341)
Cash and cash equivalents at beginning of year	56,732	54,185	307,526
Cash and cash equivalents at end of year	$ 103,907	$ 56,732	$ 54,185