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, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	$ 7,722		$ (62,924)		$ 185,418		$ (200,743)
Gain (Loss) on Hedged Items	(7,124)		62,014		(182,571)		197,442
Net Fair Value Hedge Ineffectiveness	598	[1]	(910)	[1]	2,847	[1]	(3,301)	[1]
Derivative Net Interest Income (Expense)	(22,879)	[2]	(23,297)	[2]	(76,373)	[2]	(56,951)	[2]
Advances [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	11,284		(14,908)		173,158		(18,117)
Gain (Loss) on Hedged Items	(11,539)		14,353		(173,037)		17,006
Net Fair Value Hedge Ineffectiveness	(255)	[1]	(555)	[1]	121	[1]	(1,111)	[1]
Derivative Net Interest Income (Expense)	(32,660)	[2]	(39,967)	[2]	(107,868)	[2]	(128,105)	[2]
Available-for-sale Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(13,603)		(51,566)		152,903		(147,513)
Gain (Loss) on Hedged Items	14,650		51,536		(150,404)		147,067
Net Fair Value Hedge Ineffectiveness	1,047	[1]	(30)	[1]	2,499	[1]	(446)	[1]
Derivative Net Interest Income (Expense)	(20,117)	[2]	(18,275)	[2]	(60,327)	[2]	(52,232)	[2]
Unsecured Debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	10,041		3,550		(140,643)		(35,113)
Gain (Loss) on Hedged Items	(10,235)		(3,875)		140,870		33,369
Net Fair Value Hedge Ineffectiveness	(194)	[1]	(325)	[1]	227	[1]	(1,744)	[1]
Derivative Net Interest Income (Expense)	$ 29,898	[2]	$ 34,945	[2]	$ 91,822	[2]	$ 123,386	[2]

[1] Reported as net gains (losses) on derivatives and hedging activities in the statements of income.

[2] The net interest income (expense) associated with derivatives in ASC 815 fair value hedging relationships is reported in the statements of income in the interest income/expense line item for the indicated hedged item.