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Fair Value of Financial Instruments - Contractual Maturity (Details) $ in Thousands | Sep. 30, 2017 USD ($)
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Schedule of Available-for-sale Securities [Line Items] |
Mature within One Year | $ 214,516
After One Year through Two Years | 28,037
Over Two Years | 10,015
Fair Value | 252,568
Commercial paper |
Schedule of Available-for-sale Securities [Line Items] |
Mature within One Year | 20,933
After One Year through Two Years | 0
Over Two Years | 0
Fair Value | 20,933
US government agencies |
Schedule of Available-for-sale Securities [Line Items] |
Mature within One Year | 159,019
After One Year through Two Years | 0
Over Two Years | 0
Fair Value | 159,019
Corporate bonds |
Schedule of Available-for-sale Securities [Line Items] |
Mature within One Year | 32,783
After One Year through Two Years | 27,037
Over Two Years | 9,449
Fair Value | 69,269
Asset backed securities |
Schedule of Available-for-sale Securities [Line Items] |
Mature within One Year | 1,781
After One Year through Two Years | 1,000
Over Two Years | 566
Fair Value | $ 3,347

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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=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 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=73527792&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=66010992&loc=d3e26610-111562 + Details
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