Offsetting of Assets and Liabilities (Details) - USD ($) $ in Thousands		Sep. 30, 2016		Dec. 31, 2015
Offsetting of Assets and Liabilities [Line Items]
Financial derivatives–assets, at fair value-	[1]	$ 64,817		$ 162,905
Financial derivatives–liabilities, at fair value-	[1]	(39,816)		(60,472)
Fair value repurchase agreements	[1]	165,048		105,700
Reverse Repurchase Agreements	[1]	(983,814)		(1,174,189)
Derivative Liability Instruments available for offset		(29,593)		(18,644)
Reverse Repurchase Agreements Available for Offset		(165,048)		(105,700)
Derivative Asset Instruments available for offset		29,593		18,644
Repurchase Agreements Available for Offset		165,048		105,700
Repurchase Agreements and Related Collateral Net		0		0
Reverse Repurchase Agreements and Related Collateral Net		0		0
Securities Collateral relating to Reverse Repurchase Agreements		1,120,000		1,360,000
Financial Derivatives - Assets [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial derivatives–assets, at fair value-		64,817	[2]	162,905	[3]
Financial Instruments Pledged as Collateral	[4],[5]	0		0
Cash collateral received	[4],[5]	(13,319)		(105,202)
Derivatives and Related Collateral Net		21,905		39,059
Excess cash collateral		11,200		4,100
Repurchase Agreements [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial Instruments Pledged as Collateral	[4],[5]	0		0
Cash collateral received	[4],[5]	0		0
Reverse Repurchase Agreements [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial Instruments Pledged as Collateral	[4],[5]	818,766		1,042,947
Cash collateral pledged	[4],[5]	0		25,542
Financial Derivatives - Liabilities [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial derivatives–liabilities, at fair value-		(39,816)	[2]	(60,472)	[3]
Financial Instruments Pledged as Collateral	[4],[5]	0		0
Cash collateral pledged	[4],[5]	10,223		41,699
Derivatives and Related Collateral Net		0		(129)
Excess cash collateral		$ 25,900		$ 45,800

[1] In the Company's Consolidated Statement of Assets, Liabilities, and Equity, all balances associated with repurchase agreements, reverse repurchase agreements, and financial derivatives are presented on a gross basis.

[2] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.

[3] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.

[4] For the purpose of this presentation, for each row the total amount of financial instruments transferred or pledged and cash collateral (received) or pledged may not exceed the applicable gross amount of assets or (liabilities) as presented here. Therefore, the Company has reduced the amount of financial instruments transferred or pledged as collateral related to the Company's reverse repurchase agreements and cash collateral pledged on the Company's financial derivative liabilities. Total financial instruments transferred or pledged as collateral on the Company's reverse repurchase agreements as of September 30, 2016 and December 31, 2015 were $1.12 billion and $1.36 billion, respectively. As of September 30, 2016 and December 31, 2015, total cash collateral on financial derivative assets excludes excess net cash collateral pledged of $11.2 million and $4.1 million, respectively. As of September 30, 2016 and December 31, 2015, total cash collateral on financial derivative liabilities excludes excess cash collateral pledged of $25.9 million and $45.8 million, respectively.

[5] When collateral is pledged to or pledged by a counterparty, it is often pledged or posted with respect to all positions with such counterparty, and in such cases such collateral cannot be specifically identified as relating to a specific asset or liability. As a result, in preparing the above tables, the Company has made assumptions in allocating pledged or posted collateral among the various rows.