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Pensions And Other Postretirement Benefits (Narrative) (Details) (USD $)
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1 Months Ended | 12 Months Ended | 12 Months Ended | ||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Feb. 28, 2010
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2011
Pension Benefits [Member]
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Dec. 31, 2010
Pension Benefits [Member]
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Dec. 31, 2009
Pension Benefits [Member]
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Dec. 31, 2011
Other Benefits [Member]
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Dec. 31, 2010
Other Benefits [Member]
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Dec. 31, 2011
SEI Opportunity Collective Fund [Member]
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Dec. 31, 2011
SEI Special Situations Fund [Member]
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Dec. 31, 2011
Structured Credit [Member]
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Dec. 31, 2011
Real Estate [Member]
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Dec. 31, 2011
North American Coal [Member]
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Dec. 31, 2010
North American Coal [Member]
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Dec. 31, 2009
North American Coal [Member]
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Dec. 31, 2011
Defined Benefit Postretirement Health Coverage [Member]
United States Postretirement Benefit Plans Of U S Entity Defined Benefit [Member]
Prior To Age 65 [Member]
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Dec. 31, 2011
Defined Benefit Postretirement Health Coverage [Member]
United States Postretirement Benefit Plans Of U S Entity Defined Benefit [Member]
After Age 65 [Member]
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Dec. 31, 2011
Defined Benefit Postretirement Health Coverage [Member]
Northshore [Member]
After Age 65 [Member]
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Dec. 31, 2011
United States [Member]
Pension Benefits [Member]
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Dec. 31, 2010
United States [Member]
Pension Benefits [Member]
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Dec. 31, 2011
United States [Member]
Other Benefits [Member]
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Dec. 31, 2010
United States [Member]
Other Benefits [Member]
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Dec. 31, 2011
Canada [Member]
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Dec. 31, 2011
Canada [Member]
Pension Benefits [Member]
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Dec. 31, 2010
Canada [Member]
Pension Benefits [Member]
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Dec. 31, 2011
Canada [Member]
Other Benefits [Member]
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Dec. 31, 2010
Canada [Member]
Other Benefits [Member]
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Dec. 31, 2011
Lower Limit [Member]
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Dec. 31, 2011
Lower Limit [Member]
Defined Benefit Postretirement Health Coverage [Member]
Northshore [Member]
Prior To Age 65 [Member]
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Dec. 31, 2011
Upper Limit [Member]
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Dec. 31, 2011
Upper Limit [Member]
Defined Benefit Postretirement Health Coverage [Member]
Northshore [Member]
Prior To Age 65 [Member]
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| Defined Benefit Plan Disclosure [Line Items] | |||||||||||||||||||||||||||||||
| Remaining interest percentage | 73.20% | ||||||||||||||||||||||||||||||
| Number of USW Employees | 2,400 | ||||||||||||||||||||||||||||||
| Percentage of total workforce under labor contract | 32.00% | 11.00% | |||||||||||||||||||||||||||||
| Annual limit on medical coverage for each participant | $ 7,000 | $ 3,000 | $ 2,000 | $ 4,020 | $ 4,500 | ||||||||||||||||||||||||||
| Minimum participants percentage | 15.00% | ||||||||||||||||||||||||||||||
| Contribution rate per hour worked | 6.50 | 6.42 | 5.27 | ||||||||||||||||||||||||||||
| Annual costs for defined contribution plan | 5,700,000 | 4,200,000 | 2,100,000 | 9,500,000 | 10,300,000 | 6,100,000 | |||||||||||||||||||||||||
| Funding of bargaining unit pension plans and VEBAs | 90,000,000 | ||||||||||||||||||||||||||||||
| Accumulated benefit obligation for defined benefit pension plans | 1,114,700,000 | 997,200,000 | |||||||||||||||||||||||||||||
| Redemption request notice period, days | 65 | 95 | 90 | 45 | |||||||||||||||||||||||||||
| Discount rate | 4.28% | 5.11% | 4.28% | 5.11% | 4.28% | 5.11% | 4.00% | 4.00% | 5.00% | 4.25% | 5.00% | 4.12% | 4.43% | ||||||||||||||||||
| Investment Commitments Reserved | 13,000,000 | ||||||||||||||||||||||||||||||
| Reserved investment commitments | 10,500,000 | ||||||||||||||||||||||||||||||
| Contributions by participants to other benefit plans | $ 4,600,000 | $ 6,200,000 | |||||||||||||||||||||||||||||