Percentage Of Natural Gas Purchases For Which The Company's Exposure To Fluctuations In Gas Prices Have Been Reduced.

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Percentage of Electricity Purchases For Which The Company's Exposure To Fluctuations In Electricity Prices Have Been Reduced

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The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Face (par) amount of debt instrument at time of issuance.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Average contractual rate at which a foreign currency can be purchased or sold.

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Nominal or face amount used to calculate payments on the derivative liability.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The amount of net gains or losses on foreign currency cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

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The net gain (loss) during the reporting period due to ineffectiveness in foreign currency cash flow hedges. Recognized in earnings.

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Amount before tax, after reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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Derivative Financial Instruments and Related Hedging Programs, Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2015	Mar. 31, 2010
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (3,400,000)	$ (6,800,000)	$ 3,900,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	(300,000)	0	$ 0
Aggregate fair value of derivative instruments in a net liability position	(14,600,000)
Derivative Asset	$ 1,600,000	85,700,000
2016
Derivative [Line Items]
Percentage Of Natural Gas Purchases For Which The Company's Exposure To Fluctuations In Gas Prices Have Been Reduced	73.00%
Percentage of Electricity Purchases For Which Company Exposure To Fluctuations In Electricity Prices Have Been Reduced	55.00%
2017
Derivative [Line Items]
Percentage Of Natural Gas Purchases For Which The Company's Exposure To Fluctuations In Gas Prices Have Been Reduced	72.00%
2018
Derivative [Line Items]
Percentage Of Natural Gas Purchases For Which The Company's Exposure To Fluctuations In Gas Prices Have Been Reduced	59.00%
Purchase \| Designated as Hedging Instrument \| Swap contracts \| Foreign Currency
Derivative [Line Items]
Derivative Liability, Notional Amount	$ 4,700,000	$ 0
Derivative, Average Forward Exchange Rate	1.1453
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	$ 0
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	0
Unrealized Gain (Loss) on Derivatives	(300,000)
Gain (Loss) on Foreign Currency Cash Flow Hedge Ineffectiveness	$ 0
Purchase \| Designated as Hedging Instrument \| Swap contracts \| Minimum \| Foreign Currency
Derivative [Line Items]
Derivative, Remaining Maturity	1 month
Purchase \| Designated as Hedging Instrument \| Swap contracts \| Maximum \| Foreign Currency
Derivative [Line Items]
Derivative, Remaining Maturity	12 months
Convertible Notes \| Convertible Notes Payable
Derivative [Line Items]
Principal amount of notes					$ 175,000,000
Derivative Asset				$ 94,900,000