Offsetting of Assets and Liabilities (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
Offsetting Assets and Liabilities [Line Items]
Securities Collateral Relating To Repurchase Agreements	$ 1,390,000,000		$ 1,360,000,000
Financial derivatives–assets, at fair value	3,072,000	[1]	34,963,000	[1]
Derivative Liability, Fair Value, Amount Offset Against Collateral	(2,722,000)		(1,042,000)
Reverse repurchase agreements	13,987,000	[1]	0
Securities sold under agreements to repurchase available for offset	(13,987,000)
Financial derivatives-liabilities, at fair value	(8,700,000)	[1]	(1,069,000)	[1]
Derivative Asset, Fair Value, Amount Offset Against Collateral	2,722,000		1,042,000
Repurchase agreements	(1,323,080,000)	[1]	(1,310,347,000)	[1]
Securities purchased under agreements to resell available for offset	13,987,000		0
Derivative Financial Instruments, Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Derivatives and related collateral, net	350,000		11,561,000
Financial Instruments Pledged as Collateral	0	[2],[3]	0	[2],[4]
Cash Collateral (Received) Pledged	0	[2],[3]	(22,360,000)	[2],[4]
Excess cash collateral	500,000		300,000
Reverse Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Financial Instruments Pledged as Collateral	0	[2],[3]
Cash Collateral (Received) Pledged	0	[2],[3]
Reverse Repurchase Agreements and Related Collateral Net	0
Derivative Financial Instruments, Liabilities [Member]
Offsetting Assets and Liabilities [Line Items]
Derivatives and related collateral, net	(195,000)		(1,000)
Financial Instruments Pledged as Collateral	0	[2],[3]	0	[2],[4]
Cash Collateral (Received) Pledged	5,783,000	[2],[3]	26,000	[2],[4]
Excess cash collateral	6,300,000		3,100,000
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Repurchse agreements and related collateral, net	0		0
Financial Instruments Pledged as Collateral	1,303,360,000	[2],[3]	1,295,567,000	[2],[4]
Cash Collateral (Received) Pledged	$ 5,733,000	[2],[3]	$ 14,780,000	[2],[4]

[1] In the Company's Consolidated Balance Sheet, all balances associated with the repurchase agreements and financial derivatives are presented on a gross basis.

[2] 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 table, the Company has made assumptions in allocating pledged or posted collateral among the various rows.

[3] 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 repurchase agreements and cash collateral pledged on the Company's financial derivative assets and liabilities. Total financial instruments transferred or pledged as collateral on the Company's repurchase agreements as of December 31, 2014 were $1.39 billion. As of December 31, 2014 total cash collateral on financial derivative assets and financial derivative liabilities excludes $0.5 million and $6.3 million of net excess cash collateral.

[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 repurchase agreements and cash collateral pledged on the Company's financial derivative assets and liabilities. Total financial instruments transferred or pledged as collateral on the Company's repurchase agreements as of December 31, 2013 were $1.36 billion. As of December 31, 2013 total cash collateral on financial derivative assets and liabilities excludes $0.3 million and $3.1 million, respectively of net excess cash collateral.