RESIDENTIAL MORTGAGE INVESTMENTS - Schedule of Residential Mortgage Investments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 13,563,393	$ 13,222,629
Investment Premiums		436,815	432,744
Amortized Cost Basis		14,000,208	13,655,373
Carrying Amount	[1]	$ 14,154,737	$ 13,908,104
Net WAC	[2]	2.57%	2.54%
Average Yield	[2]	1.55%	1.69%
Agency Securities [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 13,557,738	$ 13,215,738
Investment Premiums		436,772	432,696
Amortized Cost Basis		13,994,510	13,648,434
Carrying Amount	[1]	$ 14,149,039	$ 13,901,165
Net WAC	[2]	2.57%	2.54%
Average Yield	[2]	1.55%	1.69%
Agency Securities [Member] | Fixed-Rate [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 796	$ 1,660
Investment Premiums		2	4
Amortized Cost Basis		798	1,664
Carrying Amount	[1]	$ 799	$ 1,665
Net WAC	[2]	6.61%	6.63%
Average Yield	[2]	6.11%	6.45%
Agency Securities [Member] | ARMs [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 10,014,401	$ 10,230,419
Investment Premiums		317,545	328,781
Amortized Cost Basis		10,331,946	10,559,200
Carrying Amount	[1]	$ 10,487,785	$ 10,800,332
Net WAC	[2]	2.55%	2.51%
Average Yield	[2]	1.63%	1.72%
Agency Securities [Member] | Ginnie Mae ARMs [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 3,542,541	$ 2,983,659
Investment Premiums		119,225	103,911
Amortized Cost Basis		3,661,766	3,087,570
Carrying Amount	[1]	$ 3,660,455	$ 3,099,168
Net WAC	[2]	2.61%	2.63%
Average Yield	[2]	1.30%	1.53%
Residential Mortgage Loans [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 3,805	$ 4,894
Investment Premiums		12	15
Amortized Cost Basis		3,817	4,909
Carrying Amount	[1]	$ 3,817	$ 4,909
Net WAC	[2]	4.65%	4.95%
Average Yield	[2]	3.83%	3.97%
Residential Mortgage Loans [Member] | Fixed-Rate [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 1,155	$ 1,848
Investment Premiums		1	2
Amortized Cost Basis		1,156	1,850
Carrying Amount	[1]	$ 1,156	$ 1,850
Net WAC	[2]	6.76%	6.96%
Average Yield	[2]	5.12%	5.46%
Residential Mortgage Loans [Member] | ARMs [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 2,650	$ 3,046
Investment Premiums		11	13
Amortized Cost Basis		2,661	3,059
Carrying Amount	[1]	$ 2,661	$ 3,059
Net WAC	[2]	3.73%	3.73%
Average Yield	[2]	3.20%	3.14%
Collateral for Structured Financings [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Unpaid Principal Balance		$ 1,850	$ 1,997
Investment Premiums		31	33
Amortized Cost Basis		1,881	2,030
Carrying Amount	[1]	$ 1,881	$ 2,030
Net WAC	[2]	8.12%	8.11%
Average Yield	[2]	7.81%	7.62%

[1] Includes unrealized gains and losses for residential mortgage investments classified as available-for-sale.

[2] Net WAC, or weighted average coupon, is the weighted average interest rate of the mortgage loans underlying the indicated investments net of servicing and other fees as of the indicated balance sheet date. Net WAC is expressed as a percentage calculated on an annualized basis on the unpaid principal balances of the mortgage loans underlying these investments. Average yield is presented for the year then ended, and is based on the cash component of interest income expressed as a percentage calculated on an annualized basis on average amortized cost basis (the "cash yield") less the effects of amortizing investment premiums. Investment premium amortization is determined using the interest method and incorporates actual and anticipated future mortgage prepayments.