Benefit Plans (Schedule of Amounts Recognized in Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	$ 1,909	$ 2,303
Cumulative net loss	117,664	86,381
Total amount recognized	119,573	88,684
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	(4,794)	0
Cumulative net loss	4,624	3,160
Total amount recognized	$ (170)	$ 3,160