Benefit Obligations and Plan Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation	$ 388,589,000	$ 352,915,000
Service cost	2,252,000	2,889,000	8,127,000
Interest cost	19,500,000	19,761,000	21,919,000
Plan Participants' contributions	0	0
Amendments	0	353,000
Actuarial loss	62,722,000	34,687,000
Curtailment gain	(13,939,000)	0
Benefits Paid	(23,506,000)	(22,016,000)
Defined Benefit Plan, Benefit Obligation	435,618,000	388,589,000	352,915,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	277,598,000	255,327,000
Actual gain (loss) on plan assets	(4,718,000)	37,853,000
Employer contribution	28,626,000	6,434,000
Plan Participants' contributions	0	0
Benefits Paid	(23,506,000)	(22,016,000)
Defined Benefit Plan, Fair Value of Plan Assets	278,000,000	277,598,000	255,327,000
Funded status - under	(157,618,000)	(110,991,000)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Other accrued Liabilities (current)	0	0
Other liabilities (noncurrent)	(157,618,000)	(110,991,000)
Net amount recognized	(157,618,000)	(110,991,000)
Actuarial loss	189,494,000	117,840,000
Prior service cost (credit)	(632,000)	631,000
Transition obligation	0	0
Total	188,862,000	118,471,000
Defined Benefit Plan, Accumulated Benefit Obligation	435,600,000	374,500,000
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Projected Benefit Obligation	435,618,000	388,589,000
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation	435,618,000	374,538,000
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets	278,000,000	277,598,000
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation	91,286,000	88,151,000
Service cost	1,443,000	1,357,000	2,206,000
Interest cost	4,700,000	4,817,000	5,465,000
Plan Participants' contributions	2,644,000	2,500,000
Amendments	0	121,000
Actuarial loss	17,940,000	3,228,000
Curtailment gain	0	0
Benefits Paid	(7,324,000)	(8,888,000)
Defined Benefit Plan, Benefit Obligation	110,689,000	91,286,000	88,151,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	70,610,000	66,984,000
Actual gain (loss) on plan assets	(872,000)	7,278,000
Employer contribution	3,027,000	2,736,000
Plan Participants' contributions	2,644,000	2,500,000
Benefits Paid	(7,324,000)	(8,888,000)
Defined Benefit Plan, Fair Value of Plan Assets	68,085,000	70,610,000	66,984,000
Funded status - under	(42,604,000)	(20,676,000)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Other accrued Liabilities (current)	(550,000)	(525,000)
Other liabilities (noncurrent)	(42,054,000)	(20,151,000)
Net amount recognized	(42,604,000)	(20,676,000)
Actuarial loss	43,861,000	20,751,000
Prior service cost (credit)	(8,615,000)	(11,292,000)
Transition obligation	2,128,000	4,253,000
Total	$ 37,374,000	$ 13,712,000