Repurchase Agreements, net (Details) - Securities Purchased and Sold Under Repurchase Agreements (USD $)	Jun. 30, 2014		Dec. 31, 2013
Reverse Repurchase Agreements
Gross Amounts of Assets	$ 1,028,661,000
Gross Amounts offset in the Condensed Consolidated Balance Sheet	(1,028,661,000)
Net Amounts of Assets Presented in the Condensed Consolidated Balance Sheet	0
Amounts Not Offset in the Condensed Consolidated Balance Sheet, Financial Instruments	0
Amounts Not Offset in the Condensed Consolidated Balance Sheet, Cash Collateral Held	0
Net Amount	0
Repurchase Agreements
Gross Amounts of Liabilities	(15,422,241,000)
Gross Amounts offset in the Condensed Consolidated Balance Sheet	1,028,661,000
Net Amounts of Liabilities Presented in the Condensed Consolidated Balance Sheet	(14,393,580,000)		(13,151,504,000)
Amounts Not Offset in the Condensed Consolidated Balance Sheet, Financial Instruments	14,393,580,000	[1]
Amounts Not Offset in the Condensed Consolidated Balance Sheet, Cash Collateral Posted	(62,959,000)
Net Amount	(62,959,000)
Pledged securities, fair value	$ 16,284,466,000		$ 13,832,482,000

[1] The fair value of securities pledged against our repurchase agreements was $16,284,466 at June 30, 2014.