Derivatives and Hedging Activities (Derivatives in Statement of Income) (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]
Net gains (losses) related to derivatives not designated as hedging instruments	$ 2,153	$ (1,400)	$ (650)	$ (2,045)
Net gains (losses) on derivatives and hedging activities	3,482	(5,285)	2,641	(5,178)
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value hedge ineffectiveness	1,329	(3,885)	3,291	(3,133)
Interest Rate Swap [Member] | Economic Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) related to derivatives not designated as hedging instruments	(575)	300	(2,000)	473
Interest Rate Caps and Floors [Member] | Economic Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) related to derivatives not designated as hedging instruments	(231)	(2,813)	(2,272)	(4,972)
Net Interest Settlements [Member] | Economic Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) related to derivatives not designated as hedging instruments	268	(337)	(1,122)	(10)
Mortgage Delivery Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) related to derivatives not designated as hedging instruments	2,687	1,445	4,732	2,236
Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) related to derivatives not designated as hedging instruments	$ 4	$ 5	$ 12	$ 228