Fair Value of Financial Instruments - Additional Information (Detail)	Sep. 30, 2013 USD ($)	Sep. 30, 2013 GBP (£)	Dec. 31, 2012 USD ($)
Fair Value Disclosures [Abstract]
Transfers of financial instruments between levels	$ 0		$ 0
Transfers of financial insturments between level 2 to level 1	0		0
Transfers of financial insturments out of level 3	0		0
Notional value of foreign currency forward		£ 80,000,000

Fair Value, Assets, Level 3 Transfers, Amount

No definition available.

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

+ Details

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- Details

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- Definition

Aggregate notional amount of foreign currency exchange rate derivatives. Notional amount refers to the number of currency units specified in the foreign currency derivative contract.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

+ Details

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