Marketable Securities and Fair Value Measurements - Schedule of Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Assets
Marketable Securities	$ 83,973	$ 85,372
Total	123,892	114,347
Level 1
Financial Assets
Total	39,919	28,975
Level 2
Financial Assets
Total	83,973	85,372
Cash
Financial Assets
Cash and Cash Equivalents	27,346	18,672
Cash \| Level 1
Financial Assets
Cash and Cash Equivalents	27,346	18,672
Cash equivalents
Financial Assets
Cash and Cash Equivalents	12,573	10,303
Cash equivalents \| Level 1
Financial Assets
Cash and Cash Equivalents	12,573	10,303
Certificates of deposit
Financial Assets
Marketable Securities	15,993	12,508
Certificates of deposit \| Level 2
Financial Assets
Marketable Securities	15,993	12,508
Corporate securities
Financial Assets
Marketable Securities	40,940	42,732
Corporate securities \| Level 2
Financial Assets
Marketable Securities	40,940	42,732
U.S. Treasury and agency securities
Financial Assets
Marketable Securities	3,482	5,176
U.S. Treasury and agency securities \| Level 2
Financial Assets
Marketable Securities	3,482	5,176
Commercial paper
Financial Assets
Marketable Securities	9,216	11,469
Commercial paper \| Level 2
Financial Assets
Marketable Securities	9,216	11,469
Asset-backed securities
Financial Assets
Marketable Securities	14,342	13,487
Asset-backed securities \| Level 2
Financial Assets
Marketable Securities	$ 14,342	$ 13,487

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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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)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash
-URI http://asc.fasb.org/extlink&oid=6506951

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6507016

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