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Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category Short-Term and Long-Term Securities (Detail) - USD ($) $ in Thousands | Jun. 30, 2015 | Dec. 31, 2014
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Short-Term Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | $ 177,523 | $ 129,600
Investments, Gross Unrealized Gains | 39 | 16
Investments, Gross Unrealized (Losses) | (129) | (22)
Investments, Estimated Fair Value | 177,433 | 129,594
Short-Term Investments [Member] | Time Deposits and Certificates of Deposit [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 23,630 | 20,901
Investments, Gross Unrealized (Losses) |  | (1)
Investments, Estimated Fair Value | 23,630 | 20,900
Short-Term Investments [Member] | Asset-Backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 256 |
Investments, Gross Unrealized (Losses) | (101) |
Investments, Estimated Fair Value | 155 |
Short-Term Investments [Member] | Bankers' Acceptance Drafts [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 222 | 82
Investments, Estimated Fair Value | 222 | 82
Short-Term Investments [Member] | Commercial Paper [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 3,449 |
Investments, Gross Unrealized Gains | 1 |
Investments, Estimated Fair Value | 3,450 |
Short-Term Investments [Member] | Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 59,735 | 24,029
Investments, Gross Unrealized Gains | 7 | 2
Investments, Gross Unrealized (Losses) | (23) | (11)
Investments, Estimated Fair Value | 59,719 | 24,020
Short-Term Investments [Member] | Municipal Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 7,055 | 2,100
Investments, Gross Unrealized Gains | 6 |
Investments, Gross Unrealized (Losses) | (4) | (1)
Investments, Estimated Fair Value | 7,057 | 2,099
Short-Term Investments [Member] | U.S. Agency Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 83,176 | 82,488
Investments, Gross Unrealized Gains | 25 | 14
Investments, Gross Unrealized (Losses) | (1) | (9)
Investments, Estimated Fair Value | 83,200 | 82,493
Long-Term Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 257,017 | 157,489
Investments, Gross Unrealized Gains | 73 | 8
Investments, Gross Unrealized (Losses) | (235) | (296)
Investments, Estimated Fair Value | 256,855 | 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 | 140,695 | 75,778
Investments, Gross Unrealized Gains | 50 | 5
Investments, Gross Unrealized (Losses) | (68) | (109)
Investments, Estimated Fair Value | 140,677 | 75,674
Long-Term Investments [Member] | Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 103,709 | 64,842
Investments, Gross Unrealized Gains | 17 | 1
Investments, Gross Unrealized (Losses) | (156) | (174)
Investments, Estimated Fair Value | 103,570 | 64,669
Long-Term Investments [Member] | Municipal Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 615 | 1,258
Investments, Gross Unrealized (Losses) | (10) | (4)
Investments, Estimated Fair Value | 605 | 1,254
Long-Term Investments [Member] | U.S. Agency Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 11,998 | 15,563
Investments, Gross Unrealized Gains | 6 | 2
Investments, Gross Unrealized (Losses) | (1) | (9)
Investments, Estimated Fair Value | $ 12,003 | $ 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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