Transactions with Related Parties (Transactions with Other FHLBanks) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Related Party Transaction [Line Items]
Interest income on MPF loans	$ 41,284	$ 49,880	$ 128,788	$ 153,863
FHLBank of Chicago [Member]
Related Party Transaction [Line Items]
Servicing fee expense	190	169	545	500
Interest income on MPF loans	3	0	6	4
Interest-bearing deposits maintained with FHLBank of Chicago	$ 11,164		$ 11,164		$ 16,180

Income from servicing real estate mortgages, credit cards, and other financial assets held by others. Also include any premiums received in lieu of regular servicing fees on such loans only as earned over the life of the loans. May also be net of any related impairment of fair value of capitalized service costs.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Article 9

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 13

-Chapter V

-Subsection II

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13 (d))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Name:	us-gaap_ServicingFeesNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration