Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category Short-Term Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Investments, Estimated Fair Value	$ 430,663	$ 286,795
Time Deposits and Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Estimated Fair Value	11,892	20,948
Bankers Acceptance Drafts [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Estimated Fair Value	728	82
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Estimated Fair Value	124,997	75,674
Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Estimated Fair Value	165,109	88,689
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Estimated Fair Value	8,355	3,353
U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Estimated Fair Value	119,582	98,049
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	431,382	287,088
Investments, Gross Unrealized Gains	21	24
Investments, Gross Unrealized (Losses)	(740)	(317)
Investments, Estimated Fair Value	430,663	286,795
Short-Term Investments [Member] \| Time Deposits and Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	11,893	20,949
Investments, Gross Unrealized (Losses)	(1)	(1)
Investments, Estimated Fair Value	11,892	20,948
Short-Term Investments [Member] \| Bankers Acceptance Drafts [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	728	82
Investments, Estimated Fair Value	728	82
Short-Term Investments [Member] \| Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	125,271	75,778
Investments, Gross Unrealized Gains		5
Investments, Gross Unrealized (Losses)	(274)	(109)
Investments, Estimated Fair Value	124,997	75,674
Short-Term Investments [Member] \| Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	165,445	88,871
Investments, Gross Unrealized Gains	5	3
Investments, Gross Unrealized (Losses)	(341)	(185)
Investments, Estimated Fair Value	165,109	88,689
Short-Term Investments [Member] \| Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	8,346	3,357
Investments, Gross Unrealized Gains	13
Investments, Gross Unrealized (Losses)	(4)	(4)
Investments, Estimated Fair Value	8,355	3,353
Short-Term Investments [Member] \| U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	119,699	98,051
Investments, Gross Unrealized Gains	3	16
Investments, Gross Unrealized (Losses)	(120)	(18)
Investments, Estimated Fair Value	$ 119,582	$ 98,049

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=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

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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
-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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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
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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