Derivatives and Hedging Activities (Derivatives in Statement of Income) (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]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ 598	$ (910)	$ 2,847	$ (3,301)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(1,261)	(6,198)	1,366	(1,269)
Gain (Loss) on Derivative Instruments, Net, Pretax	(663)	(7,108)	4,213	(4,570)
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	601	(896)	2,850	(3,213)
Interest Rate Swap [Member] | Advances [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	139	2	190	50
Interest Rate Swap [Member] | Unsecured Debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(154)	395	(769)	2,653
Interest Rate Swap [Member] | Discount Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	0	784
Interest Rate Swap [Member] | Basis Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(1,270)	(8,383)	(452)	(7,878)
Interest Rate Swap [Member] | Intermediary Transactions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(7)	(3)	4	(7)
Interest Rate Swaptions Related to Optional Advance Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	(199)	0	(1,933)
Interest Rate Cap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	(3)	(14)	(3)	(88)
Interest Rate Cap [Member] | Held-to-maturity Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(661)	(501)	(565)	(3,301)
Interest Rate Cap [Member] | Intermediary Transactions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	0	6
Net Interest Income on Interest Rate Swaps [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 692	$ 2,491	$ 2,958	$ 8,357