Benefit Plans (Schedule of Net Funded Status) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 54	$ 61
Interest cost	886	959
Plan amendments	(4,794)	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer Contributions	10,000	20,000	10,000
Fair value of plan assets, ending balance	153,604
Defined Benefit Plan, Funded Status of Plan [Abstract]
Prepaid (accrued) pension/postretirement cost	220,900	190,800
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Prepaid (accrued) pension/postretirement cost	220,900	190,800
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(90,046)	(58,793)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected Benefit Obligation, Beginning Balance	211,183	193,359
Service cost	6,123	5,919	5,290
Interest cost	11,439	11,200	11,003
Plan amendments	0	0
Participant contributions	0	0
Actuarial gain	23,727	8,512
Benefits paid	(8,832)	(7,807)
Projected Benefit Obligation, Ending Balance	243,640	211,183	193,359
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	152,390	122,799
Actual return on plan assets	(1,352)	16,130
Participant contributions	0	0
Employer Contributions	11,399	21,268
Benefits paid	(8,832)	(7,807)
Fair value of plan assets, ending balance	153,605	152,390	122,799
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded Status	(90,046)	(58,793)
Prior service costs	1,909	2,303
Cumulative net loss	117,664	86,381
Prepaid (accrued) pension/postretirement cost	29,527	29,891
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Funded Status	(90,046)	(58,793)
Intangible asset	0	0
Accumulated other comprehensive income	119,573	88,684
Prepaid (accrued) pension/postretirement cost	29,527	29,891
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(16,250)	(19,942)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected Benefit Obligation, Beginning Balance	19,942	19,675
Service cost	54	61	173
Interest cost	886	959	1,412
Participant contributions	846	509
Actuarial gain	1,578	954
Benefits paid	(2,262)	(2,216)
Projected Benefit Obligation, Ending Balance	16,250	19,942	19,675
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	0	0
Actual return on plan assets	0	0
Participant contributions	846	509
Employer Contributions	1,416	1,707
Benefits paid	(2,262)	(2,216)
Fair value of plan assets, ending balance	0	0	0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded Status	(16,250)	(19,942)
Prior service costs	(4,794)	0
Cumulative net loss	4,624	3,160
Prepaid (accrued) pension/postretirement cost	(16,420)	(16,782)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Funded Status	(16,250)	(19,942)
Intangible asset	0	0
Accumulated other comprehensive income	(170)	3,160
Prepaid (accrued) pension/postretirement cost	$ (16,420)	$ (16,782)