Derivatives and Hedging Activities Derivatives in Statement of Income and Impact on Interest (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	$ 31,773		$ 77,781
Gain (Loss) on Hedged Item	(28,851)		(74,327)
Net Fair Value Hedge Ineffectiveness	2,922		3,454
Effect of Derivatives on Net Interest Income	(20,264)	[1]	(72,224)	[1]
Advances [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	40,420		76,502
Gain (Loss) on Hedged Item	(37,783)		(72,716)
Net Fair Value Hedge Ineffectiveness	2,637		3,786
Effect of Derivatives on Net Interest Income	(28,752)	[1]	(81,105)	[1]
Consolidated Obligation Bonds [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	(8,647)		1,279
Gain (Loss) on Hedged Item	8,932		(1,611)
Net Fair Value Hedge Ineffectiveness	285		(332)
Effect of Derivatives on Net Interest Income	$ 8,488	[1]	$ 8,881	[1]

[1] The net interest on derivatives in fair value hedge relationships is included in the interest income/expense line item of the respective hedged item.