Employee Benefit Plans (Combined Activity In The Corporation's Defined Benefit Pension Plans) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Benefit Plans [Abstract]
Benefit obligation at beginning of year	$ 145,246	$ 132,456	$ 120,730
Interest cost	7,892	7,724	7,973
Actuarial (gain) loss	10,383	10,189	8,512
Benefit obligation at end of year	157,855	145,246	132,456
Fair value of plan assets at beginning of year	141,050	128,044	106,489
Actual return on plan assets	(3,776)	17,580	25,795
Employer contributions	5,645	549	519
Benefits paid	(5,666)	(5,123)	(4,759)
Fair value of plan assets at end of year	137,253	141,050	128,044
Funded status of the plan at end of year and accrued benefit liability recognized	20,602	4,196	4,412
Accumulated benefit obligation at end of year	$ 157,855	$ 145,246	$ 131,863