Consolidated Obligations (Consolidated Obligation Discount Notes) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Short-term Debt [Line Items]
Book value	$ 20,888,257		$ 10,921,498
Discount Notes [Member]
Short-term Debt [Line Items]
Par value	$ 20,893,996		$ 10,922,000
Weighted average interest rate	0.13%	[1]	0.03%	[1]

[1] Represents an implied rate.