Short-term Investments - Summary of Investments in a Continuous Loss Position (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair value	$ 38,790
Less Than 12 Months, Gross unrealized losses	(29)
12 Months or Greater, Fair value	0
12 Months or Greater, Gross unrealized losses	0
Total, Fair value	38,790
Total, Gross unrealized losses	29
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair value	28,800
Less Than 12 Months, Gross unrealized losses	(17)
12 Months or Greater, Fair value	0
12 Months or Greater, Gross unrealized losses	0
Total, Fair value	28,800
Total, Gross unrealized losses	17
U.S. government-related debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair value	9,990
Less Than 12 Months, Gross unrealized losses	(12)
12 Months or Greater, Fair value	0
12 Months or Greater, Gross unrealized losses	0
Total, Fair value	9,990
Total, Gross unrealized losses	$ 12

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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-Name Accounting Standards Codification
-Topic 320
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