Derivatives and Hedging Activities Derivatives in Statement of Condition (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	$ 2,544,546		$ 3,897,588
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	2,412		2,841
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	11,057		16,514
Notional Amount of Derivatives	8,972,421		12,159,963
Derivative Asset, Fair Value, Gross Asset	59,236		69,677
Derivative Liability, Fair Value, Gross Liability	342,996		389,473
Derivative assets	4,834		5,877
Derivative liabilities	108,930		114,888
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount of Fair Value Hedge Instruments	6,427,875		8,262,375
Derivative Instruments in Hedges, Assets, at Fair Value	56,824		66,836
Derivative Instruments in Hedges, Liabilities, at Fair Value	331,939		372,959
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	2,433,000		3,774,000
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	2,289		2,686
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	10,698		15,930
Mortgage Delivery Commitments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	111,546		123,588
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	123		155
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	359		584
Netting Adjustment By Counterparty [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	(52,802)		(61,900)
Derivative Liability, Fair Value, Amount Offset Against Collateral	(52,802)		(61,900)
Cash Collateral And Related Accrued Interest [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	(1,600)		(1,900)
Derivative Liability, Fair Value, Amount Offset Against Collateral	(181,264)		(212,685)
Netting and Collateral [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	(54,402)	[1]	(63,800)	[1]
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ (234,066)	[1]	$ (274,585)	[1]

[1] Amounts represent the effects of legally enforceable master netting agreements that allow the FHLBank to settle positive and negative positions and of cash collateral held or placed with the same counterparties.