Components of Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets related to:
Employee benefits	$ 74,288	$ 31,067
Inventories	64,484us-gaap_DeferredTaxAssetsInventory	53,229us-gaap_DeferredTaxAssetsInventory
Valuation and other reserves	48,278	18,372
Net operating loss carryforwards	171,781	5,379
Cumulative noncurrent deferred tax assets at end of period	70,367	31,467	73,588
Other items, net	14,191us-gaap_DeferredTaxAssetsOther
Gross deferred tax assets	443,389us-gaap_DeferredTaxAssetsGross	139,514us-gaap_DeferredTaxAssetsGross
Valuation allowance on deferred tax assets	(6,133)	(5,858)
Total net deferred tax assets	437,256us-gaap_DeferredTaxAssetsNet	133,656us-gaap_DeferredTaxAssetsNet
Deferred tax liabilities related to:
Property, plant and equipment	(638,730)	(257,366)
Goodwill and other intangibles	(288,471)	(78,577)
Other items, net		(2,891)us-gaap_DeferredTaxLiabilitiesOther
Total deferred tax liabilities	(927,201)us-gaap_DeferredIncomeTaxLiabilities	(338,834)us-gaap_DeferredIncomeTaxLiabilities
Net deferred tax liability	$ (489,945)us-gaap_DeferredTaxLiabilities	$ (205,178)us-gaap_DeferredTaxLiabilities

Deferred tax assets, valuation and other reserves.

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from inventory.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from employee benefit costs not otherwise specified in the taxonomy, which can only be deducted for tax purposes when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount of deferred tax liability attributable to taxable temporary differences net of deferred tax asset attributable to deductible temporary differences and carryforwards after valuation allowances.

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Amount of deferred tax liability attributable to taxable temporary differences from intangible assets including goodwill.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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