Derivatives and Hedging Activities (Details 1) (Not Designated as Hedging Instrument [Member], USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Notional values or contractual amounts and fair value of the Corporation's derivatives not designated in hedge relationships
Derivative Asset, Notional/Contract Amount	$ 1,081,846	$ 1,009,901	$ 1,054,049
Derivative Asset, Fair Value	47,809	47,764	51,611
Derivative Liability, Notional/Contract Amount	909,640	837,961	796,956
Derivative Liability, Fair Value	46,265	44,274	49,493
Interest rate swaps [Member]
Notional values or contractual amounts and fair value of the Corporation's derivatives not designated in hedge relationships
Derivative Asset, Notional/Contract Amount	863,344	774,623	717,915
Derivative Asset, Fair Value	46,246	44,270	49,391
Derivative Liability, Notional/Contract Amount	863,344	774,623	717,915
Derivative Liability, Fair Value	46,246	44,270	49,391
Mortgage loan commitments [Member]
Notional values or contractual amounts and fair value of the Corporation's derivatives not designated in hedge relationships
Derivative Asset, Notional/Contract Amount	129,909	118,119	200,883
Derivative Asset, Fair Value	1,539	1,384	4,057
Derivative Liability, Notional/Contract Amount	0	0	0
Derivative Liability, Fair Value	0	0	0
Forward sales contracts [Member]
Notional values or contractual amounts and fair value of the Corporation's derivatives not designated in hedge relationships
Derivative Asset, Notional/Contract Amount	84,517	113,426	132,084
Derivative Asset, Fair Value	5	2,106	(1,939)
Derivative Liability, Notional/Contract Amount	0	0	0
Derivative Liability, Fair Value	0	0	0
Credit contracts [Member]
Notional values or contractual amounts and fair value of the Corporation's derivatives not designated in hedge relationships
Derivative Asset, Notional/Contract Amount	0	0	0
Derivative Asset, Fair Value	0	0	0
Derivative Liability, Notional/Contract Amount	24,714	44,983	61,175
Derivative Liability, Fair Value	0	0	0
Foreign exchange [Member]
Notional values or contractual amounts and fair value of the Corporation's derivatives not designated in hedge relationships
Derivative Asset, Notional/Contract Amount	4,076	3,733	3,167
Derivative Asset, Fair Value	19	4	102
Derivative Liability, Notional/Contract Amount	4,076	3,733	3,167
Derivative Liability, Fair Value	19	4	102
Other [Member]
Notional values or contractual amounts and fair value of the Corporation's derivatives not designated in hedge relationships
Derivative Asset, Notional/Contract Amount	0	0	0
Derivative Asset, Fair Value	0	0	0
Derivative Liability, Notional/Contract Amount	17,506	14,622	14,699
Derivative Liability, Fair Value	$ 0	$ 0	$ 0