Pensions and Other Postretirement Benefit Plans (Schedule of Funded Status of Plans) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 304,658	$ 262,376	$ 247,072
Benefit obligation	405,880	374,115	353,971
Funded status	(101,222)	(111,739)
Noncurrent asset	7,779	715
Current liability	(3,576)	(3,764)
Noncurrent liability	(105,425)	(108,690)
Net amount recognized	(101,222)	(111,739)
Net actuarial loss	164,246	150,062
Prior service cost/(credit)	432	480
Transition obligation	138	240
Net amount recognized	164,816	150,782
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Benefit obligation	79,009	72,137	73,208
Funded status	(79,009)	(72,137)
Noncurrent asset
Current liability	(5,949)	(6,223)
Noncurrent liability	(73,060)	(65,914)
Net amount recognized	(79,009)	(72,137)
Net actuarial loss	54,835	50,884
Prior service cost/(credit)	(43,995)	(47,662)
Transition obligation
Net amount recognized	$ 10,840	$ 3,222