Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 76,402	$ 85,049
Gross Unrealized Gain	4,552	11,163
Gross Unrealized (Loss)	(12)	(49)
Fair Value	80,942	96,163
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	105	59,302
Fair Value	105	59,302
United States government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,974
Gross Unrealized Gain	8
Fair Value	18,982
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	57,323	25,747
Gross Unrealized Gain	57
Gross Unrealized (Loss)	(12)	(49)
Fair Value	57,368	25,698
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Gain	4,487	11,163
Fair Value	$ 4,487	$ 11,163

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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