CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Cash Flows From Operating Activities:
Net income	$ 322,393	$ 312,668	$ 313,226
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of MBS and U.S. Treasury securities	(39,577)	(35,837)	(34,900)
Gain on sales of real estate owned	(4,475)	(3,229)	(76)
Gain on liquidation of residential whole loans	(11,868)	0	0
Other-than-temporary impairment charges	1,032	485	705
Accretion of purchase discounts on MBS and CRT securities, residential whole loans and MSR related assets	(86,318)	(84,615)	(95,377)
Amortization of purchase premiums on MBS and CRT securities	30,330	36,725	41,624
Depreciation and amortization on real estate, fixed assets and other assets	1,519	964	860
Equity-based compensation expense	8,033	9,162	7,832
Unrealized gain on residential whole loans at fair value	(33,617)	(31,254)	(6,532)
Increase in other assets and other	(5,569)	(23,122)	(5,407)
(Decrease)/increase in other liabilities	(5,813)	(6,943)	56,170
Net cash provided by operating activities	176,070	175,004	278,125
Cash Flows From Investing Activities:
Principal payments on MBS, CRT securities and MSR related assets	3,996,489	3,339,597	2,916,807
Proceeds from sales of MBS and U.S. Treasury securities	243,081	85,594	70,747
Purchases of MBS, CRT securities, MSR related assets, and U.S. Treasury Securities	(1,583,130)	(1,995,013)	(1,810,303)
Purchases of residential whole loans and capitalized advances	(1,065,981)	(677,003)	(617,017)
Principal payments on residential whole loans	160,469	103,997	51,427
Proceeds from sales of real estate owned	75,671	34,200	4,049
Purchases of real estate owned and capital improvements	(19,801)	(2,825)	0
Redemption of Federal Home Loan Bank stock	10,422	51,400	0
Purchases of Federal Home Loan Bank stock	0	(1,805)	(60,017)
Additions to leasehold improvements, furniture and fixtures	(872)	(708)	(1,560)
Net cash provided by investing activities	1,816,348	937,434	554,133
Cash Flows From Financing Activities:
Principal payments on repurchase agreements and other advances	(72,563,218)	(82,408,484)	(92,012,931)
Proceeds from borrowings under repurchase agreements and other advances	70,490,091	81,706,806	91,614,851
Proceeds from issuance of securitized debt	382,847	0	0
Principal payments on securitized debt	(16,562)	(22,057)	(88,347)
Payments made for securitization related costs	(2,646)	0	0
Payments made for margin calls and settlements on repurchase agreements and interest rate swap agreements (“Swaps”)	(46,022)	(177,363)	(267,200)
Proceeds from reverse margin calls and settlements on repurchase agreements and Swaps	79,517	192,000	215,100
Proceeds from issuances of common stock	196,808	4,660	1,218
Dividends paid on preferred stock	(15,000)	(15,000)	(15,000)
Dividends paid on common stock and dividend equivalents	(308,588)	(297,895)	(297,379)
Net cash used in financing activities	(1,802,773)	(1,017,333)	(849,688)
Net increase/(decrease) in cash and cash equivalents	189,645	95,105	(17,430)
Cash and cash equivalents at beginning of period	260,112	165,007	182,437
Cash and cash equivalents at end of period	449,757	260,112	165,007
Supplemental Disclosure of Cash Flow Information
Interest Paid	198,159	194,626	172,919
Non-cash Investing and Financing Activities:
MBS and CRT securities recorded upon adoption of revised accounting standard for repurchase agreement financing	0	0	1,917,813
Repurchase agreements recorded upon adoption of revised accounting standard for repurchase agreement financing	0	0	1,519,593
Net increase in securities obtained as collateral/obligation to return securities obtained as collateral	134,100	5,385	32,670
Transfer from residential whole loans to real estate owned	136,734	91,896	30,104
Dividends and dividend equivalents declared and unpaid	$ 79,771	$ 74,657	$ 74,575