Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Commitments and Contingencies [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 892,963	$ 1,228,375
Other FHLBanks [Member]
Commitments and Contingencies [Line Items]
Debt, Gross	692,000,000
Loan Origination Commitments [Member]
Commitments and Contingencies [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Asset	18,240	77,212
Standby Letters of Credit [Member]
Commitments and Contingencies [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Asset	$ 2,840,755	$ 2,947,267

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226016-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (d)(2)

-URI http://asc.fasb.org/extlink&oid=20225523&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41678-113959

Name:	us-gaap_DerivativeCollateralRightToReclaimCash
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant