Employee Benefits (Other Comprehensive Income, Other Postretirement Benefit Plans) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss (gain)	$ (2,109)	$ (77,678)	$ (9,874)
Prior service benefit, arising during period	0	0	26,605
Net gain (loss)	11,971	6,505	3,374
Total recognized in other comprehensive income	4,100	(76,985)	17,351
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss (gain)	(5,900)	34,517	(4,792)
Prior service benefit, arising during period	0	0	(26,605)
Prior service benefit	5,877	5,927	2,869
Net gain (loss)	(615)	39	175
Total recognized in other comprehensive income	$ (638)	$ 40,483	$ (28,353)