Investments - Investments Reported in Other Current and Non-Current Assets (Detail) (USD $)
In Millions, unless otherwise specified |
Dec. 31, 2012
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Dec. 31, 2011
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Schedule of Equity Method Investments [Line Items] | ||
Funding Commitments | $ 7.2 | |
Assets | 54.1 | 53.8 |
Chem-Mod LLC [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Assets | 4.0 | |
Chem-Mod International LLC [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Assets | 2.0 | |
Clean-Coal Investments [Member] | Twelve 2009 Era Clean Coal Production Plants [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Funding Commitments | 0.4 | |
Assets | 7.8 | 8.9 |
Clean-Coal Investments [Member] | Two 2009 Era Clean Coal Plants [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Assets | 1.3 | 1.5 |
Clean-Coal Investments [Member] | Five 2011 Era Clean Coal Production Plants [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Assets | 13.2 | |
Clean-Coal Investments [Member] | Ten 2011 Era Clean Coal Production Plants [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Funding Commitments | 3.9 | |
Assets | 14.3 | 33.4 |
Clean-Coal Investments [Member] | Notes Receivable and Interest from Co-Investor [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Assets | 8.5 | 8.0 |
Other Investments [Member]
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Schedule of Equity Method Investments [Line Items] | ||
Funding Commitments | 2.9 | |
Assets | $ 3.0 | $ 2.0 |