Fair Value Disclosures - Fair Value Measurements, Recurring and Nonrecurring (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	$ 7,318		$ 19,718
Security Sold, Not yet Purchased	1,673,532		0
Financial derivatives, Liabilities	54,474		64,388
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	1,065,993		755,633
Trading securities	0		0
Marketable Securities	1,065,993		755,633
Derivative Asset	0		0
Assets at fair value	1,065,993		755,633
Financial derivatives, Liabilities	62		1
Liabilities at fair value	1,673,594		1
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	1,194,799		1,662,024
Trading securities	0		0
Marketable Securities	1,194,799		1,662,024
Derivative Asset	7,318		19,718
Assets at fair value	1,202,117		1,681,742
Financial derivatives, Liabilities	78,234		75,472
Liabilities at fair value	78,234		75,472
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	55,171		65,490
Trading securities	880		928
Marketable Securities	56,051		66,418
Derivative Asset	0		0
Assets at fair value	5,176,636		6,770,031
Financial derivatives, Liabilities	0		235
Liabilities at fair value	0		235
Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	2,315,963		2,483,147
Trading securities	880		928
Marketable Securities	2,316,843		2,484,075
Derivative Asset	7,318		19,718
Assets at fair value	7,444,746		9,207,406
Financial derivatives, Liabilities	78,296		75,708
Liabilities at fair value	1,751,828		75,708
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	5,765		6,238
Fair Value, Measurements, Nonrecurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	5,765		6,238
Farmer Mac Guaranteed Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Farmer Mac Guaranteed Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Farmer Mac Guaranteed Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	3,437,556		5,091,600
Farmer Mac Guaranteed Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	3,437,556		5,091,600
Farmer Mac Guaranteed Securities AgVantage [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Farmer Mac Guaranteed Securities AgVantage [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Farmer Mac Guaranteed Securities AgVantage [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	3,416,512		5,070,366
Farmer Mac Guaranteed Securities AgVantage [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	3,416,512		5,070,366
Farmer Mac Guaranteed USDA Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Farmer Mac Guaranteed USDA Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Farmer Mac Guaranteed USDA Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	21,044		21,234
Farmer Mac Guaranteed USDA Securities [Member] | Farmer Mac Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	21,044		21,234
loans held for investment [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	0		0
loans held for investment [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	0		0
loans held for investment [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	5,003		4,420
loans held for investment [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	5,003		4,420
REO [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	0		0
REO [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	0		0
REO [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	762		1,818
REO [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	762		1,818
USDA Securities [Member] | USDA Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Trading securities	0		0
Marketable Securities	0		0
USDA Securities [Member] | USDA Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Trading securities	0		0
Marketable Securities	0		0
USDA Securities [Member] | USDA Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	1,636,930		1,553,669
Trading securities	46,099		58,344
Marketable Securities	1,683,029		1,612,013
USDA Securities [Member] | USDA Guarantee [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	1,636,930		1,553,669
Trading securities	46,099		58,344
Marketable Securities	1,683,029		1,612,013
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	54,976		65,285
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	54,976		65,285
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	54,976		65,285
Floating Interest Rate [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	120,244		166,104
Trading securities	880		928
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	120,244		166,104
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	120,244		166,104
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Trading Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	0		0
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Trading Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	0		0
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Trading Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	880		928
Floating Interest Rate [Member] | Asset-backed Securities [Member] | Trading Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	880		928
Floating Interest Rate [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	26,688		109,769
Floating Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	26,688		109,769
Floating Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	26,688		109,769
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	626,544		621,269
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	626,349		621,064
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	195		205
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	626,544		621,269
Floating Interest Rate [Member] | Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	63,385		63,385
Floating Interest Rate [Member] | Subordinated Debt [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Subordinated Debt [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	63,385		63,385
Floating Interest Rate [Member] | Subordinated Debt [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Floating Interest Rate [Member] | Subordinated Debt [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	63,385		63,385
Floating Interest Rate [Member] | Taxable Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value			30,681
Floating Interest Rate [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	74,998
Floating Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	74,998
Floating Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0
Floating Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0
Floating Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	74,998
Fixed Interest Rate [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	55,170		55,141
Fixed Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	55,170		55,141
Fixed Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	55,170		55,141
Fixed Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	8,460	[1]	8,657
Fixed Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	8,460		8,657
Fixed Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	8,460		8,657
Fixed Interest Rate [Member] | Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	82,425		83,161
Fixed Interest Rate [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	82,425		83,161
Fixed Interest Rate [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	82,425		83,161
Fixed Interest Rate [Member] | Taxable Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	11,978
Fixed Interest Rate [Member] | Taxable Municipal Bonds [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Taxable Municipal Bonds [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	11,978		30,681
Fixed Interest Rate [Member] | Taxable Municipal Bonds [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Taxable Municipal Bonds [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	11,978		30,681
Fixed Interest Rate [Member] | Senior Agency Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	200,100		524,062
Fixed Interest Rate [Member] | Senior Agency Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Senior Agency Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	200,100		524,062
Fixed Interest Rate [Member] | Senior Agency Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | Senior Agency Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	200,100		524,062
Fixed Interest Rate [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	990,995		755,633
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	990,995		755,633
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	0		0
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale, at fair value	990,995		755,633
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Security Sold, Not yet Purchased	1,673,532
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Security Sold, Not yet Purchased	0
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Security Sold, Not yet Purchased	0
Fixed Interest Rate [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Security Sold, Not yet Purchased	$ 1,673,532

[1] (1)Fair value includes $7.4 million of an interest-only security with a notional amount of $152.4 million.