Derivative Instruments and Risk Management - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Derivative [Line Items]
Derivatives, determination of fair value	The fair values of the derivative instruments disclosed above were measured based on Level 2 inputs.
Designated as Hedging Instrument
Derivative [Line Items]
Derivative hedging agreements covering diesel fuel requirements	45.00%
Derivative hedging agreements covering diesel fuel requirements, year 2014	34.00%
Designated as Hedging Instrument \| Foreign Exchange Contract
Derivative [Line Items]
Face value of unexpired foreign currency contracts	$ 25.6

Describes how an entity determines the fair values of its derivatives, including its valuation methodology and significant assumptions used.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(n))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph n

-Article 4

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2229141

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration