Employee Benefits (Other Comprehensive Income - Retirement Plans) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss	$ 77,678	$ 9,874	$ 48,580
Net loss	6,505	3,374	1,625
Net loss	0	(26,605)	0
Prior service cost	(5,812)	(2,754)	(2,754)
Total expense recognized in other comprehensive income	(76,985)	17,351	(49,709)
Retirement Income Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss	40,181	12,844	48,531
Net loss	(6,190)	(3,331)	(1,549)
Prior service cost	(21)	(21)	(21)
Total expense recognized in other comprehensive income	33,970	9,492	46,961
Non-Qualified Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss	2,980	1,822	1,892
Net loss	(354)	(218)	(76)
Prior service cost	(94)	(94)	(94)
Total expense recognized in other comprehensive income	$ 2,532	$ 1,510	$ 1,722