Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Taxes [Line Items]
Benefit from (provision for) income taxes	$ 5,842	$ (154)	$ 5,328	$ (379)
Tax benefit related to unrealized gain associated with change in market value of marketable securities	6,100		$ 6,100
Tax benefit, minimum percentage of likelihood of being realized upon ultimate settlement			50.00%
Available-for-sale Securities
Income Taxes [Line Items]
Accumulated other comprehensive income, before tax	$ 15,138		$ 15,138

Represents minimum percentage of likelihood of tax benefit being realized upon ultimate settlement.

No definition available.

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- Definition

Income Taxes [Line Items]

+ References

No definition available.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a),(b)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

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.(h))

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Income Tax Expense (or Benefit)

-URI http://asc.fasb.org/extlink&oid=6515339

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- Definition

The sum of income tax expense or benefit for the period that has been allocated among continuing operations, discontinued operations, extraordinary items, other comprehensive income, and items charged or credited directly to shareholders' equity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 20

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=18498875&loc=d3e38679-109324

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