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Summary of significant accounting policies (Tables) | 12 Months Ended
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Dec. 31, 2011
Summary of significant accounting policies [Abstract] |
Estimate useful life of property, plant and equipment by category | Depreciation of plant and equipment is provided for by the straight-line method over the following estimated useful lives:
| Buildings and improvements: | 14 to 45 years
| Machinery and equipment: | 5 to 22 years
Carrying amount and fair value of debt | The following table provides the carrying amounts and approximate fair value (based the last available trading data) of our 8.0% senior notes due 2014 (the “8.0% Notes”), our 7.5% senior unsecured notes due 2014 (the “7.5% Notes”) and our 1.75% convertible senior notes due 2024 (the “1.75% Notes”).
|  | December 31, 2011 |  |  | December 31, 2010 |
|  | Carrying amount |  |  | Fair value |  |  | Carrying amount |  |  | Fair value |
8.0% Notes |  | $ | 246,909 |  |  | $ | 249,292 |  |  | $ | 245,927 |  |  | $ | 249,604 |
7.5% Notes |  |  | 2,603 |  |  |  | 2,564 |  |  |  | 2,603 |  |  |  | 2,541 |
1.75% Notes |  |  | –– |  |  |  | - |  |  |  | 45,483 |  |  |  | 46,588 |

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- Definition Tabula disclosure of the estimated useful life of property, plant, and equipment by category. + References No definition available. + Details
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- Definition Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(e),(f)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644 Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644 + Details
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