Financial Instruments - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2015 USD ($) MMBTU $ / MMBTU	Sep. 30, 2015 USD ($) MMBTU $ / MMBTU
Derivative [Line Items]
Amount of losses, net of income taxes, reclassified to earnings from change in fair value of derivatives component of accumulated other comprehensive loss	$ 300	$ 1,200
Estimated reclassification of losses, net of income taxes, from the change in fair value of derivatives component of accumulated other comprehensive loss to earnings during the next twelve months	1,000
Interest rate and natural gas swap [Member]
Derivative [Line Items]
Derivative liabilities	2,100	2,100
Interest Rate Swap [Member]
Derivative [Line Items]
Aggregate notional principal amount of outstanding interest rate swap agreements	100,000	100,000
Net payments under derivative swap agreements	300	1,100
Natural Gas [Member]
Derivative [Line Items]
Net payments under derivative swap agreements	$ 200	$ 800
Principal amount of natural gas swap agreements (mmbtu) \| MMBTU	1,764,000	1,764,000
Hedged portion of estimated twelve month exposure to natural gas price fluctuations (percent)	41.00%	41.00%
Foreign Currency Exchange Rate Risk [Member]
Derivative [Line Items]
Foreign currency gains of net investment hedges included in accumulated other comprehensive loss	$ 400	$ 19,500
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Derivative [Line Items]
Cash and cash equivalents	104,203	104,203
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative liabilities	1,465	1,465
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative liabilities	626	626
Estimate of Fair Value, Fair Value Disclosure [Member]
Derivative [Line Items]
Cash and cash equivalents	104,203	104,203
Estimate of Fair Value, Fair Value Disclosure [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative liabilities	1,465	1,465
Estimate of Fair Value, Fair Value Disclosure [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative liabilities	626	626
Bank debt [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	1,131,814	1,131,814
Bank debt [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	1,131,814	1,131,814
5 1/2% Senior Notes [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	300,000	300,000
5 1/2% Senior Notes [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	310,410	310,410
5% Senior Notes [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	500,000	500,000
5% Senior Notes [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	$ 503,750	$ 503,750
Natural Gas [Member] \| Minimum [Member] \| Natural Gas [Member]
Derivative [Line Items]
Natural gas fixed price (per mmbtu) \| $ / MMBTU	2.86	2.86
Natural Gas [Member] \| Maximum [Member] \| Natural Gas [Member]
Derivative [Line Items]
Natural gas fixed price (per mmbtu) \| $ / MMBTU	4.16	4.16
Accrued Liabilities [Member] \| Interest rate and natural gas swap [Member]
Derivative [Line Items]
Derivative liabilities	$ 1,700	$ 1,700
Other Liabilities [Member] \| Interest rate and natural gas swap [Member]
Derivative [Line Items]
Derivative liabilities	$ 400	$ 400

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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-Publisher FASB

-Name Accounting Standards Codification

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Fair value of all liability derivatives designated as cash flow hedging instruments.

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The premium (cost) of a hedge, net of any cash received on settlement during the period.

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The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings.

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The percentage of expected requirements covered by the aggregate notional amount of derivative contracts expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract as a percentage of expected need.

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- Definition

Fixed price related to the price risk swap derivative.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Amount before tax, after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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