Affordable Housing Program (AHP) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Affordable Housing Program [Roll Forward]
AHP Obligation, Beginning Balance	$ 82,672
AHP, Expense (Current Year Additions)	7,237	6,796
AHP, Subsidy Uses, Net	(2,395)	(2,454)
AHP Obligation, Ending Balance	$ 87,514

The amount of the obligation related to Affordable Housing Program (AHP) assessments, as required by the Federal Home Loan Bank Act of 1932. These AHP funds provide subsidies to members to assist in the purchase, construction, or rehabilitation of housing for very low-, low-, and moderate-income households.

No definition available.

Name:	us-gaap_AffordableHousingProgramObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant