Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

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Average fixed interest rate related to the group of interest rate derivatives.

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Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of derivative instruments of a particular group held by the entity.

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Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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The carrying amount, as of the date of the latest financial statement presented, of all assets that are pledged as collateral for the payment of the related debt obligation primarily arising from secured borrowings, repurchase agreements or other current or potential obligations, where the secured party does not have the right by contract or custom to sell or re-pledge the collateral and therefore are not reclassified and separately reported in the statement of financial position.

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Other Assets - Derivative Instruments (Details 2) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) derivative	Sep. 30, 2016 USD ($) derivative	Sep. 30, 2017 USD ($) derivative	Sep. 30, 2016 USD ($) derivative	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Assets pledged	$ 8,473,834		$ 8,473,834		$ 10,620,406
Number of terminated derivatives \| derivative	0	0	0	0
Interest expense attributable to Swaps	$ 49,275	$ 48,167	$ 148,646	$ 143,487
AOCI from derivative hedging instruments:
Balance at beginning of period	(35,841)	(131,971)	(46,721)	(69,399)
Net gain/(loss) on Swaps	5,791	22,769	16,671	(39,803)
Balance at end of period	(30,050)	(109,202)	(30,050)	(109,202)
Interest Rate Contract
Derivative [Line Items]
Assets pledged	29,721		29,721		86,317
Interest Rate Contract \| Agency MBS, at fair value
Derivative [Line Items]
Assets pledged	23,197		23,197		32,468
Interest Rate Contract \| Restricted cash
Derivative [Line Items]
Assets pledged	6,524		6,524		53,849
Swaps, at fair value
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 2,550,000		$ 2,550,000		$ 2,900,000
Weighted average fixed-pay rate	2.04%		2.04%		1.87%
Weighted Average Variable Interest Rate	1.24%		1.24%		0.72%
Interest expense attributable to Swaps	$ 5,310	$ 10,170	$ 19,606	$ 31,279
Weighted average Swap rate paid	2.04%	1.82%	1.96%	1.82%
Weighted average Swap rate received	1.23%	0.49%	1.00%	0.45%
Swaps, at fair value \| Within 30 days
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 0		$ 0		$ 0
Weighted average fixed-pay rate	0.00%		0.00%		0.00%
Weighted Average Variable Interest Rate	0.00%		0.00%		0.00%
Swaps, at fair value \| Over 30 days to 3 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 0		$ 0		$ 50,000
Weighted average fixed-pay rate	0.00%		0.00%		0.67%
Weighted Average Variable Interest Rate	0.00%		0.00%		0.64%
Swaps, at fair value \| Over 3 months to 6 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 0		$ 0		$ 300,000
Weighted average fixed-pay rate	0.00%		0.00%		0.57%
Weighted Average Variable Interest Rate	0.00%		0.00%		0.66%
Swaps, at fair value \| Over 6 months to 12 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 550,000		$ 550,000		$ 0
Weighted average fixed-pay rate	1.49%		1.49%		0.00%
Weighted Average Variable Interest Rate	1.23%		1.23%		0.00%
Swaps, at fair value \| Over 12 months to 24 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 200,000		$ 200,000		$ 550,000
Weighted average fixed-pay rate	1.71%		1.71%		1.49%
Weighted Average Variable Interest Rate	1.24%		1.24%		0.71%
Swaps, at fair value \| Over 24 months to 36 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 1,500,000		$ 1,500,000		$ 200,000
Weighted average fixed-pay rate	2.22%		2.22%		1.71%
Weighted Average Variable Interest Rate	1.24%		1.24%		0.76%
Swaps, at fair value \| Over 36 months to 48 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 200,000		$ 200,000		$ 1,500,000
Weighted average fixed-pay rate	2.20%		2.20%		2.22%
Weighted Average Variable Interest Rate	1.23%		1.23%		0.74%
Swaps, at fair value \| Over 48 months to 60 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 0		$ 0		$ 200,000
Weighted average fixed-pay rate	0.00%		0.00%		2.20%
Weighted Average Variable Interest Rate	0.00%		0.00%		0.75%
Swaps, at fair value \| Over 60 months to 72 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 100,000		$ 100,000		$ 0
Weighted average fixed-pay rate	2.75%		2.75%		0.00%
Weighted Average Variable Interest Rate	1.24%		1.24%		0.00%
Swaps, at fair value \| Over 72 months to 84 months
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 0		$ 0		$ 100,000
Weighted average fixed-pay rate	0.00%		0.00%		2.75%
Weighted Average Variable Interest Rate	0.00%		0.00%		0.74%
Swaps, at fair value \| Over 84 Months
Derivative [Line Items]
Number of instruments held \| derivative	1		1
Swaps, at fair value \| Hedging
Derivative [Line Items]
Aggregate notional amount of derivatives	$ 2,600,000		$ 2,600,000
Average maturity term of swaps			30 months
Swaps, at fair value \| Minimum \| LIBOR
Derivative [Line Items]
Derivative, variable interest rate, term			1 month
Swaps, at fair value \| Maximum \| Hedging
Derivative [Line Items]
Maximum maturity term of swaps			71 months
Swaps, at fair value \| Maximum \| LIBOR
Derivative [Line Items]
Derivative, variable interest rate, term			3 months
New Swaps
Derivative [Line Items]
Number of new Swaps \| derivative	0		0
Aggregate notional amount	$ 0		$ 0
Swaps amortized expired
Derivative [Line Items]
Aggregate notional amount	$ 0		$ 350,000
Swaps amortized expired \| QTD
Derivative [Line Items]
Weighted average fixed-pay rate	0.00%		0.00%
Swaps amortized expired \| YTD
Derivative [Line Items]
Weighted average fixed-pay rate	0.58%		0.58%