Employee Benefit Plans Employee Benefit Plans and Components of Net Periodic Postretirement Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 608	$ 539	$ 623
Interest cost	6,832	7,393	7,456
Expected return on assets	(9,855)	(10,054)	(9,342)
Amortization of prior service cost	324	324	231
Amortization of actuarial loss	594	229	237
Net periodic pension credit	(1,497)	(1,569)	(795)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	161	164	177
Interest cost	170	222	219
Amortization of prior service cost	0	0	29
Amortization of actuarial loss	0	0	(16)
Net periodic pension credit	$ 331	$ 386	$ 409