Offsetting of Assets and Liabilities (Details) - USD ($) $ in Thousands		Jun. 30, 2016		Dec. 31, 2015
Offsetting of Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 152,628
Derivative Liability, Fair Value, Gross Liability		(74,098)
Repurchase Agreements, Gross		129,993
Reverse Repurchase Agreements, Gross		(1,083,940)
Financial derivatives assets gross amount offset		0
Financial derivative-liabilities gross amount offset		0
Repurchase agreements gross amount offset		(13,990)
Reverse repurchase agreements, gross amount offset		13,835
Financial derivatives–assets, at fair value-	[1]	152,628		$ 162,905
Financial derivatives–liabilities, at fair value-	[1]	(74,098)		(60,472)
Fair value repurchase agreements	[1]	116,003		105,700
Reverse Repurchase Agreements	[1]	(1,070,105)		(1,174,189)
Derivative Liability Instruments available for offset		(37,919)		(18,644)
Reverse Repurchase Agreements Available for Offset		(116,003)		(105,700)
Derivative Asset Instruments available for offset		37,919		18,644
Repurchase Agreements Available for Offset		116,003		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		1,240,000		1,360,000
Financial Derivatives - Assets [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial derivatives–assets, at fair value-		152,628	[2]	162,905	[3]
Financial Instruments Pledged as Collateral	[4],[5]	0		0
Cash collateral received	[4],[5]	(75,676)		(105,202)
Derivatives and Related Collateral Net		39,033		39,059
Excess cash collateral		11,400		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]	950,974		1,042,947
Cash collateral pledged	[4],[5]	3,128		25,542
Financial Derivatives - Liabilities [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial derivatives–liabilities, at fair value-		(74,098)	[2]	(60,472)	[3]
Financial Instruments Pledged as Collateral	[4],[5]	0		0
Cash collateral pledged	[4],[5]	36,179		41,699
Derivatives and Related Collateral Net		0		(129)
Excess cash collateral		$ 38,600		$ 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 June 30, 2016 and December 31, 2015 were $1.24 billion and $1.36 billion, respectively. As of June 30, 2016 and December 31, 2015, total cash collateral on financial derivative assets excludes excess net cash collateral pledged of $11.4 million and $4.1 million, respectively. As of June 30, 2016 and December 31, 2015, total cash collateral on financial derivative liabilities excludes excess cash collateral pledged of $38.6 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.