Employee Benefits (Other Comprehensive Income, Other Postretirement Benefit 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 (gain)	$ (77,678)	$ (9,874)	$ (48,580)
Prior service benefit, arising during period	0	26,605	0
Net gain	(5,812)	(2,754)	(2,754)
Total recognized in other comprehensive income	(76,985)	17,351	(49,709)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss (gain)	34,517	(4,792)	(1,843)
Prior service benefit, arising during period	0	(26,605)	0
Prior service benefit	5,927	2,869	2,869
Net gain	39	175	0
Total recognized in other comprehensive income	$ 40,483	$ (28,353)	$ 1,026