Derivatives and Hedging Activities (Derivatives in Statement of Income and Impact on Interest) (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
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) on Derivative	$ 78,845		$ (111,598)		$ 146,114		$ (51,189)
Gains/(Losses) on Hedged Item	(77,516)		107,713		(142,823)		48,056
Net Fair Value Hedge Ineffectiveness	1,329		(3,885)		3,291		(3,133)
Effect of Derivatives on Net Interest Income	(48,966)	[1]	(68,826)	[1]	(158,845)	[1]	(204,689)	[1]
Advances [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) on Derivative	84,204		(201,954)		166,564		(157,356)
Gains/(Losses) on Hedged Item	(83,765)		197,583		(165,389)		153,389
Net Fair Value Hedge Ineffectiveness	439		(4,371)		1,175		(3,967)
Effect of Derivatives on Net Interest Income	(93,120)	[1]	(121,460)		(289,346)	[1]	(374,229)	[1]
Consolidated Obligation Bonds [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) on Derivative	(5,359)		90,356		(20,450)		106,167
Gains/(Losses) on Hedged Item	6,249		(89,870)		22,566		(105,333)
Net Fair Value Hedge Ineffectiveness	890		486		2,116		834
Effect of Derivatives on Net Interest Income	$ 44,154	[1]	$ 52,634		$ 130,501	[1]	$ 169,540	[1]

[1] Represents the net interest settlements on derivatives in fair value hedge relationships presented in the interest income/expense line item of the respective hedged item.