Capital (Details) (USD $)	Oct. 31, 2013	Sep. 30, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Dec. 31, 2012
Capital [Line Items]
Risk Based Capital Required		$ 453,982,000				$ 404,265,000
Risk Based Capital Actual		1,808,663,000				1,793,383,000
Regulatory Capital, Required		1,252,793,000				1,430,213,000
Regulatory Capital, Actual		1,808,663,000				1,793,383,000
Regulatory Capital Ratio, Required		4.00%				4.00%
Regulatory Capital Ratio, Actual		5.77%				5.02%
Leverage Capital, Required		1,565,991,000				1,787,766,000
Leverage Capital, Actual		2,712,995,000				2,690,075,000
Leverage Ratio, Required		5.00%				5.00%
Leverage Ratio, Actual		8.66%				7.52%
Membership Investment Requirement, Percent of Members Total Assets as of Previous Calendar Year		0.04%
Membership Investment Requirement, Minimum Dollar Amount		1,000
Membership Investment Requirement, Maximum Dollar Amount		7,000,000
Activity Based Investment Requirement, Percent of Outstanding Advances		4.10%
Surplus Stock Threshold Percentage, Amount Over Minimum Investment Requirement	102.50%		102.50%	102.50%	102.50%
Minumum Stock Surplus Required For Repurchase	100,000		100,000	100,000	100,000
Repurchased Surplus Stock, Total			182,879,400	168,555,900	198,427,400
Repurchase of Equity [Member]
Capital [Line Items]
Repurchased Surplus Stock, Total	$ 224,091,800