Employee Benefits (Net Periodic Benefit Cost) (Details) (Other Postretirement Benefit Plans, Defined Benefit, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 4,378	$ 2,988	$ 3,558
Interest cost	5,651	5,379	6,664
Expected return on plan assets	(1,714)	(1,823)	(1,529)
Prior service benefit	(5,877)	(5,927)	(2,869)
Net loss (gain)	615	(39)	(175)
Net periodic benefit cost	$ 3,053	$ 578	$ 5,649