Consolidated Obligations (Interest Rate Payment Terms) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Short-term and Long-term Debt [Line Items]
Book value	$ 33,665,452	$ 35,613,036
Percent of Fixed Rate Consolidated Obligation Bonds Swapped to An Adjustable Rate	53.90%	52.60%
Percent Of Adjustable Rate Consolidated Obligation Bonds Swapped To Different Adjustable Rate	1.20%	3.20%
Percent of Short Term Debt Swapped	2.80%	0.00%
Consolidated Obligation Bonds [Member]
Schedule of Short-term and Long-term Debt [Line Items]
Par value of consolidated bonds	33,248,956	35,133,965
Bond premiums	105,053	125,933
Bond discounts	(19,704)	(23,290)
Hedging adjustments	331,147	376,428
Fixed Interest Rate [Member] | Consolidated Obligation Bonds [Member]
Schedule of Short-term and Long-term Debt [Line Items]
Par value of consolidated bonds	30,900,956	34,298,965
Step Up [Member] | Consolidated Obligation Bonds [Member]
Schedule of Short-term and Long-term Debt [Line Items]
Par value of consolidated bonds	1,488,000	215,000
Adjustable Interest Rate [Member] | Consolidated Obligation Bonds [Member]
Schedule of Short-term and Long-term Debt [Line Items]
Par value of consolidated bonds	$ 860,000	$ 620,000