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Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category Short-Term and Long-Term Securities (Detail) - USD ($) $ in Thousands | Sep. 30, 2015 | Dec. 31, 2014
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Short-Term Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | $ 196,823 | $ 129,600
Investments, Gross Unrealized Gains | 51 | 16
Investments, Gross Unrealized (Losses) | (32) | (22)
Investments, Estimated Fair Value | 196,842 | 129,594
Short-Term Investments [Member] | Time Deposits and Certificates of Deposit [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 21,152 | 20,901
Investments, Gross Unrealized (Losses) |  | (1)
Investments, Estimated Fair Value | 21,152 | 20,900
Short-Term Investments [Member] | Bankers' Acceptance Drafts [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 266 | 82
Investments, Estimated Fair Value | 266 | 82
Short-Term Investments [Member] | Commercial Paper [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 1,446 |
Investments, Estimated Fair Value | 1,446 |
Short-Term Investments [Member] | Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 75,448 | 24,029
Investments, Gross Unrealized Gains | 9 | 2
Investments, Gross Unrealized (Losses) | (24) | (11)
Investments, Estimated Fair Value | 75,433 | 24,020
Short-Term Investments [Member] | Municipal Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 4,953 | 2,100
Investments, Gross Unrealized Gains | 6 |
Investments, Gross Unrealized (Losses) |  | (1)
Investments, Estimated Fair Value | 4,959 | 2,099
Short-Term Investments [Member] | U.S. Agency Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 93,558 | 82,488
Investments, Gross Unrealized Gains | 36 | 14
Investments, Gross Unrealized (Losses) | (8) | (9)
Investments, Estimated Fair Value | 93,586 | 82,493
Long-Term Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 241,021 | 157,489
Investments, Gross Unrealized Gains | 140 | 8
Investments, Gross Unrealized (Losses) | (253) | (296)
Investments, Estimated Fair Value | 240,908 | 157,201
Long-Term Investments [Member] | Time Deposits and Certificates of Deposit [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost |  | 48
Investments, Estimated Fair Value |  | 48
Long-Term Investments [Member] | Asset-Backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 134,914 | 75,778
Investments, Gross Unrealized Gains | 71 | 5
Investments, Gross Unrealized (Losses) | (68) | (109)
Investments, Estimated Fair Value | 134,917 | 75,674
Long-Term Investments [Member] | Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 94,131 | 64,842
Investments, Gross Unrealized Gains | 39 | 1
Investments, Gross Unrealized (Losses) | (180) | (174)
Investments, Estimated Fair Value | 93,990 | 64,669
Long-Term Investments [Member] | Municipal Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 3,400 | 1,258
Investments, Gross Unrealized Gains | 27 |
Investments, Gross Unrealized (Losses) | (5) | (4)
Investments, Estimated Fair Value | 3,422 | 1,254
Long-Term Investments [Member] | U.S. Agency Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 8,576 | 15,563
Investments, Gross Unrealized Gains | 3 | 2
Investments, Gross Unrealized (Losses) |  | (9)
Investments, Estimated Fair Value | $ 8,579 | $ 15,556

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