Summary of Effective Tax Rate (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Effective Tax Rates Line Items
Provision computed at U.S. Federal statutory rate of 35%	$ 133,196	$ 85,226	$ 53,586
Alternative fuel mixture and cellulosic biofuel producer credits	81,695		(104,785)
State and local taxes, net of federal benefit	9,135	7,504	7,694
Domestic manufacturers deduction	(7,155)	(7,670)	(7,540)
Other	(132)	417	(1,286)
Total provision (benefit) for taxes	$ 216,739	$ 85,477	$ (52,331)

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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-Glossary Income Tax Expense (or Benefit)

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to the deduction for qualified production activities received under enacted tax laws.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The sum of other amounts reflected in the reconciliation of the statutory tax provision (benefit) to the actual tax provision (benefit).

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