Offsetting Assets and Liabilities (Details) (USD $)	6 Months Ended
	Jun. 30, 2014 counterparty		Dec. 31, 2013
Swaps, at fair value
Gross Amounts of Recognized Assets	$ 2,755,000		$ 13,000,000
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	2,755,000		13,000,000
Derivative Fair Value of Derivative Asset Gross Amounts Not Offset [Abstract]
Financial Instruments	(2,755,000)		(13,000,000)
Cash Collateral Received	0		0
Net Amount	0		0
Swaps, at fair value
Gross Amounts of Recognized Liabilities	57,426,000	[1]	28,217,000	[1]
Gross Amounts Offset in the Consolidated Balance Sheet	0	[1]	0	[1]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	57,426,000	[1]	28,217,000	[1]
Gross Amounts Not Offset in the Consolidated Balance Sheet
Financial Instruments	(4,796,000)	[1],[2]	0	[1],[2]
Cash Collateral Pledged	(52,630,000)		(28,217,000)	[1],[2]
Net Amount	0	[1]	0	[1]
Repurchase agreements
Gross Amounts of Recognized Liabilities	8,384,101,000	[3]	8,339,297,000	[3]
Gross Amounts Offset in the Consolidated Balance Sheet	0	[3]	0	[3]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	8,384,101,000	[3]	8,339,297,000	[3]
Gross Amounts Not Offset in the Consolidated Balance Sheet
Financial Instruments	(8,382,301,000)	[2],[3]	(8,339,297,000)	[2],[3]
Cash Collateral Pledged	(1,800,000)	[2],[3]	0	[2],[3]
Net Amount	0	[3]	0	[3]
Total
Gross Amounts of Recognized Liabilities	8,441,527,000		8,367,514,000
Gross Amounts Offset in the Consolidated Balance Sheet	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	8,441,527,000		8,367,514,000
Gross Amounts Not Offset in the Consolidated Balance Sheet
Financial Instruments	(8,387,097,000)	[2]	(8,339,297,000)	[2]
Cash Collateral Pledged	(54,430,000)	[2]	(28,217,000)	[2]
Net Amount	0		0
Additional disclosures
Excess collateral			9,300,000
Fair value of securities pledged against the swaps	75,100,000		73,900,000
Fair value of securities pledged against the repurchase agreements	$ 10,220,000,000		$ 10,116,000,000
Number of repurchase agreement counterparties with unconditional right of setoff	1

[1] The fair value of securities pledged against the Company’s Swaps was $75.1 million and $73.9 million at June 30, 2014 and December 31, 2013, respectively.

[2] Amounts disclosed in the Financial Instruments column of the table above represents collateral pledged that is available to be offset against liability balances associated with repurchase agreement and derivative transactions. Amounts disclosed in the Cash Collateral Pledged column of the table above represents amounts pledged as collateral against derivative transactions and excludes excess collateral of $9.3 million at December 31, 2013.

[3] The fair value of securities pledged against the Company’s repurchase agreements was $10.220 billion and $10.116 billion at June 30, 2014 and December 31, 2013, respectively.