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Cash, Cash Equivalents, and Investments - Summary of Available-for-Sale Investments (Detail) $ in Thousands | Sep. 30, 2018 USD ($)
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Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | $ 702,797
Gross unrealized gains | 608
Gross unrealized losses | (1,460)
Fair value | 701,945
Agency Bonds | Short-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 2,969
Gross unrealized gains | 0
Gross unrealized losses | 0
Fair value | 2,969
Agency Bonds | Long-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 5,930
Gross unrealized gains | 10
Gross unrealized losses | 0
Fair value | 5,940
Treasury Bills |
Schedule of Available-for-sale Securities [Line Items] |
Gross unrealized losses | (298)
Treasury Bills | Short-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 193,631
Gross unrealized gains | 0
Gross unrealized losses | (284)
Fair value | 193,347
Treasury Bills | Long-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 32,718
Gross unrealized gains | 7
Gross unrealized losses | (14)
Fair value | 32,711
Corporate Bonds |
Schedule of Available-for-sale Securities [Line Items] |
Gross unrealized losses | (683)
Corporate Bonds | Short-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 138,383
Gross unrealized gains | 56
Gross unrealized losses | (340)
Fair value | 138,099
Corporate Bonds | Long-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 175,881
Gross unrealized gains | 469
Gross unrealized losses | (343)
Fair value | 176,007
Asset-Backed Securities |
Schedule of Available-for-sale Securities [Line Items] |
Gross unrealized losses | (407)
Asset-Backed Securities | Short-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 71,646
Gross unrealized gains | 1
Gross unrealized losses | (209)
Fair value | 71,438
Asset-Backed Securities | Long-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 60,276
Gross unrealized gains | 33
Gross unrealized losses | (198)
Fair value | 60,111
Sovereign Bonds |
Schedule of Available-for-sale Securities [Line Items] |
Gross unrealized losses | (53)
Sovereign Bonds | Short-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 8,172
Gross unrealized gains | 0
Gross unrealized losses | (53)
Fair value | 8,119
Sovereign Bonds | Long-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 6,286
Gross unrealized gains | 32
Gross unrealized losses | 0
Fair value | 6,318
Municipal Bonds |
Schedule of Available-for-sale Securities [Line Items] |
Gross unrealized losses | (19)
Municipal Bonds | Short-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 6,050
Gross unrealized gains | 0
Gross unrealized losses | (6)
Fair value | 6,044
Municipal Bonds | Long-Term Investments |
Schedule of Available-for-sale Securities [Line Items] |
Amortized cost | 855
Gross unrealized gains | 0
Gross unrealized losses | (13)
Fair value | $ 842

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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt 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=82897076&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 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=82897076&loc=d3e27161-111563 + Details
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- Definition This item represents the cost of debt 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 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 Reference 2: 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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