CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Cash Flows From Operating Activities:
Net income	$ 312,668	$ 313,226	$ 313,504
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of MBS	(35,837)	(34,900)	(37,497)
Gain on sales of real estate owned	(3,229)	(76)	0
Other-than-temporary impairment charges	485	705	0
Accretion of purchase discounts on MBS and CRT securities and residential whole loans	(84,615)	(95,377)	(89,182)
Amortization of purchase premiums on MBS and CRT securities	36,725	41,624	32,052
Depreciation and amortization on real estate, fixed assets and other assets	964	860	1,191
Equity-based compensation expense	9,162	7,832	8,581
Unrealized (gain)/loss on residential whole loans at fair value	(31,254)	(6,532)	96
Increase in other assets	(112,614)	(5,407)	(9,796)
(Decrease)/increase in other liabilities	(6,943)	56,170	36,864
Net cash provided by operating activities	85,512	278,125	255,813
Cash Flows From Investing Activities:
Principal payments on MBS and CRT securities	3,339,597	2,916,807	1,939,948
Proceeds from sale of MBS	85,594	70,747	123,910
Purchases of MBS and CRT securities	(1,908,346)	(1,810,303)	(1,261,646)
Purchases of residential whole loans and capitalized advances	(677,003)	(617,017)	(356,440)
Principal payments on residential whole loans	103,997	51,427	6,017
Proceeds from sales of real estate owned	34,200	4,049	0
Redemption of Federal Home Loan Bank stock	51,400	0	0
Purchases of Federal Home Loan Bank stock	(1,805)	(60,017)	0
Additions to leasehold improvements, furniture and fixtures	(708)	(1,560)	(786)
Net cash provided by investing activities	1,026,926	554,133	451,003
Cash Flows From Financing Activities:
Principal payments on repurchase agreements and other advances	(82,408,484)	(92,012,931)	(75,939,948)
Proceeds from borrowings under repurchase agreements and other advances	81,706,806	91,614,851	75,868,039
Principal payments on securitized debt	(22,057)	(88,347)	(254,078)
Cash disbursements on financial instruments underlying Linked Transactions	0	0	(6,750,803)
Cash received from financial instruments underlying Linked Transactions	0	0	6,336,872
Payments made for margin calls on repurchase agreements and interest rate swap agreements (“Swaps”)	(177,363)	(267,200)	(208,600)
Proceeds from reverse margin calls on repurchase agreements and Swaps	192,000	215,100	132,800
Proceeds from issuances of common stock	4,660	1,218	35,639
Dividends paid on preferred stock	(15,000)	(15,000)	(15,000)
Dividends paid on common stock and dividend equivalents	(297,895)	(297,379)	(294,670)
Net cash used in financing activities	(1,017,333)	(849,688)	(1,089,749)
Net increase/(decrease) in cash and cash equivalents	95,105	(17,430)	(382,933)
Cash and cash equivalents at beginning of period	165,007	182,437	565,370
Cash and cash equivalents at end of period	260,112	165,007	182,437
Supplemental Disclosure of Cash Flow Information:
Interest paid	194,626	172,919	160,935
Non-cash Investing and Financing Activities:
MBS and CRT securities recorded upon adoption of revised accounting standard for repurchase agreement financing	0	1,917,813	0
Repurchase agreements recorded upon adoption of revised accounting standard for repurchase agreement financing	0	1,519,593	0
MBS recorded upon de-linking of Linked Transactions	0	0	86,449
Repurchase agreements recorded upon de-linking of Linked Transactions	0	0	49,095
Net increase in securities obtained as collateral/obligation to return securities obtained as collateral	5,385	32,670	135,165
Transfer from residential whole loans to real estate owned	91,896	30,104	2,904
Dividends and dividend equivalents declared and unpaid	$ 74,657	$ 74,575	$ 74,529