Income Taxes - Summary of Effective Tax Rate (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Provision computed at U.S. Federal statutory rate of 35%	$ 215.0	$ 148.3	$ 131.1
Alternative fuel mixture and cellulosic biofuel producer credits	0	(166.0)	81.7
State and local taxes, net of federal benefit	20.5	13.6	8.9
Domestic manufacturers deduction	(16.5)	(11.7)	(7.2)
Other	2.7	(1.9)	0
Total provision (benefit) for taxes	$ 221.7us-gaap_IncomeTaxExpenseBenefit	$ (17.7)us-gaap_IncomeTaxExpenseBenefit	$ 214.5us-gaap_IncomeTaxExpenseBenefit
U.S. Federal statutory rate	35.00%

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

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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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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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