Convertible Debentures and Credit Arrangements - Convertible Senior Debentures due 2024 - Additional Information (Detail) (Convertible Senior Debentures due 2024 [Member], USD $)	9 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2004
Debt Instrument [Line Items]
Aggregate face value of convertible senior debentures		$ 150,000,000.0
Credit facility maturity date		Mar. 15, 2024
Fair value of Debentures outstanding	$ 400,000
Convertible senior debentures, interest payment description	semi-annually
Convertible senior debentures, convertible latest date	Mar. 14, 2024
Conversion price (in dollars per share)	$ 43.3044
Percentage of face amount which is equal to repurchase price for providing optional conversion of debentures	100.00%
Scenario One [Member]
Debt Instrument [Line Items]
Convertible senior debentures, optional repurchase date	Mar. 20, 2014
Scenario Two [Member]
Debt Instrument [Line Items]
Convertible senior debentures, optional repurchase date	Mar. 20, 2019

Debt Instrument Convertible Optional Repurchase Dates

No definition available.

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- Definition

Debt instrument future redemption price as percentage of original principal in fifth year.

+ References

No definition available.

+ Details

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- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (b)

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-Name FASB Staff Position (FSP)

-Number APB14-1

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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- Definition

Latest date when the debt instrument can be converted into equity, in CCYY-MM-DD format.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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-Topic 505

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+ Details

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- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

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-Paragraph 2

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

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+ Details

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity 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.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

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-Paragraph 10

-Subparagraph (a)

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- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

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-Topic 210

-SubTopic 10

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-Topic 942

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-Number 129

-Paragraph 2, 4

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- Details

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

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