Fair Value Measurement - Additional Information (Detail) (3.50% Convertible Senior Notes Due 2019)	0 Months Ended	12 Months Ended
Oct. 22, 2014	Dec. 31, 2014	Oct. 22, 2014
3.50% Convertible Senior Notes Due 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, interest rate	3.50%	3.50%	3.50%
Debt instrument maturity Year	Oct. 15, 2019	Oct. 15, 2019

Contractual interest rate for funds borrowed, under the debt agreement.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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