Offsetting Assets and Liabilities (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
Offsetting of Assets and Liabilities [Line Items]
Securities Collateral realting to Repurchase and Reverse Repurchase Agreements	$ 1,600,000,000		$ 1,050,000,000
Reverse Repurchase Agreements	(1,345,223,000)		(905,718,000)
Reverse Repurchase Agreements Net	(1,304,229,000)	[1]	(892,068,000)	[1]
Reverse Repurchase Agreements and Related Collateral Net	0		0
Financial derivatives-liabilities at fair value-	(33,457,000)		(15,212,000)
Financial derivatives-assets at fair value-	43,567,000		48,504,000
Fair value	40,994,000	[1]	13,650,000	[1]
Repurchase Agreements Net	0	[1]	0	[1]
Collateral for Offsetting Relating to Repurchase Agreements	0	[2],[3]	0	[2],[3]
Cash Collateral Received Pledged for Repurchase Agreements	0	[2]	0	[2]
Repurchase Agreements and Related Collateral Net	0		0
Collateral for offsetting relating to Repurchase and Reverse Repurchase Agreements	1,300,616,000	[2],[3]	887,940,000	[2],[3]
Cash Collateral (Received) Pledged, Reverse and Reverse Repurchase Agreements	3,613,000	[2]	4,128,000	[2]
Financial Derivatives - Assets [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial derivatives-assets at fair value-	43,567,000	[1],[4]	48,504,000	[1],[4]
Derivative Asset, Fair Value, Net	10,110,000	[1]	33,292,000	[1]
Securities Collateral on Derivatives	0	[2],[3]	0	[2],[3]
Cash collateral (Received) Pledged for Derivatives	33,692,000	[2]	(13,188,000)	[2]
Derivatives and Related Collateral Net	43,802,000		20,104,000
Securities Sold under Agreements to Repurchase [Member]
Offsetting of Assets and Liabilities [Line Items]
Reverse Repurchase Agreements	(1,345,223,000)	[1]	(905,718,000)	[1]
Derivative Financial Instruments, Liabilities [Member]
Offsetting of Assets and Liabilities [Line Items]
Financial derivatives-liabilities at fair value-	(33,457,000)	[1],[4]	(15,212,000)	[1],[4]
Derivative Asset, Fair Value, Net	0	[1]	0	[1]
Securities Collateral on Derivatives	0	[2],[3]	0	[2],[3]
Cash collateral (Received) Pledged for Derivatives	0	[2]	0	[2]
Derivatives and Related Collateral Net	$ 0		$ 0

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

[2] As collateral is called or posted per counterparty it is generally called or posted across all positions with each respective counterparty.

[3] Amounts disclosed in the Financial Instruments column of the table represent collateral that is available to be offset against balances associated with repurchase and reverse repurchase agreements. For the purposes of the table above, total financial instruments and cash collateral (received) pledged can not exceed the gross amount of assets and (liabilities) as presented above. Therefore we have reduced the amount of financial instruments related to our repurchase and reverse repurchase agreements in the table above. Total financial instruments for September 30, 2013 and December 31, 2012 were $1.60 billion and $1.05 billion, respectively.

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