Investments - Investments Reported in Other Current and Non-Current Assets (Parenthetical) (Detail) (Clean-Coal Investments [Member])
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12 Months Ended |
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Dec. 31, 2012
Plant
Entity
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Twelve 2009 Era Clean Coal Production Plants [Member]
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Schedule of Equity Method Investments [Line Items] | |
Number of coal plants | 12 |
Number of variable interest entities | 5,000,000 |
Two 2009 Era Clean Coal Plants [Member]
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Schedule of Equity Method Investments [Line Items] | |
Number of coal plants | 2 |
Five 2011 Era Clean Coal Production Plants [Member]
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Schedule of Equity Method Investments [Line Items] | |
Number of coal plants | 5 |
Ten 2011 Era Clean Coal Production Plants [Member]
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Schedule of Equity Method Investments [Line Items] | |
Number of coal plants | 10 |
Notes Receivable and Interest from Co-Investor [Member]
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Schedule of Equity Method Investments [Line Items] | |
Number of plants sold | 3 |