Cash, Cash Equivalents and Investments - Fair value and Amortized cost (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 157,954	$ 114,504
Cash, cash equivalents and money market funds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	157,954	114,504
Estimated Fair Value	157,954	114,504
U.S. Treasury securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	20,037
Gross Unrealized Gains	16
Estimated Fair Value	20,053
Corporate Debt Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	3,459
Estimated Fair Value	3,459
Certificates of Deposit
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	1,950
Estimated Fair Value	1,950
Total
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	183,400	114,504
Gross Unrealized Gains	16
Estimated Fair Value	183,416	114,504
Less amounts classified as cash and cash equivalents
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	157,954	114,504
Estimated Fair Value	157,954	$ 114,504
Total available-for-sale investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	25,446
Gross Unrealized Gains	16
Estimated Fair Value	$ 25,462

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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Amount 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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