Financial Instruments - Additional Information (Detail) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2016 USD ($) MMBTU $ / MMBTU	Jun. 30, 2016 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	$ 800
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	500
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	200	500
Natural Gas [Member]
Derivative [Line Items]
Net payments under derivative swap agreements	$ 300	$ 800
Principal amount of natural gas swap agreements (mmbtu) \| MMBTU	649,000	649,000
Hedged portion of estimated twelve month exposure to natural gas price fluctuations (percent)	21.00%	21.00%
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Derivative [Line Items]
Cash and cash equivalents	$ 120,467	$ 120,467
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative liabilities	858	858
Estimate of Fair Value, Fair Value Disclosure [Member]
Derivative [Line Items]
Cash and cash equivalents	120,467	120,467
Estimate of Fair Value, Fair Value Disclosure [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative liabilities	858	858
Bank debt [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	1,146,012	1,146,012
Bank debt [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Derivative [Line Items]
Long-Term Debt	1,146,012	1,146,012
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	310,875	310,875
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	$ 513,725	$ 513,725
Minimum [Member] \| Natural Gas [Member]
Derivative [Line Items]
Natural gas fixed price \| $ / MMBTU	2.92	2.92
Maximum [Member] \| Natural Gas [Member]
Derivative [Line Items]
Natural gas fixed price \| $ / MMBTU	3.21	3.21
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Derivative [Line Items]
Foreign currency gains (losses) of net investment hedges included in accumulated other comprehensive loss	$ 1,400	$ (4,800)

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
-Sentence Column B

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

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Fair value of all liability derivatives designated as cash flow hedging instruments.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
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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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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 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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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 and 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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-SubTopic 30
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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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