Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
2021 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	$ 7,500	$ 9,500
2022 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	0	65,600
Recurring [Member]
Assets [Abstract]
Cash and cash equivalents	221,680	264,325
Investments	162,222	185,621
Fair value of financial instruments	383,902	449,946
Recurring [Member] \| Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	221,680	193,312
Recurring [Member] \| United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		62,497
Investments	74,468	112,328
Recurring [Member] \| Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		501
Investments	72,435	63,710
Recurring [Member] \| Municipal Bonds [Member]
Assets [Abstract]
Investments	6,000	6,000
Recurring [Member] \| Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		8,015
Investments	9,319	3,583
Recurring [Member] \| Level 1 [Member]
Assets [Abstract]
Cash and cash equivalents	221,680	255,809
Investments	74,468	112,328
Fair value of financial instruments	296,148	368,137
Recurring [Member] \| Level 1 [Member] \| Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	221,680	193,312
Recurring [Member] \| Level 1 [Member] \| United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		62,497
Investments	74,468	112,328
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] \| Level 1 [Member] \| Municipal Bonds [Member]
Assets [Abstract]
Investments	0	0
Recurring [Member] \| Level 1 [Member] \| Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] \| Level 2 [Member]
Assets [Abstract]
Cash and cash equivalents	0	8,516
Investments	87,754	73,293
Fair value of financial instruments	87,754	81,809
Recurring [Member] \| Level 2 [Member] \| Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] \| Level 2 [Member] \| United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		501
Investments	72,435	63,710
Recurring [Member] \| Level 2 [Member] \| Municipal Bonds [Member]
Assets [Abstract]
Investments	6,000	6,000
Recurring [Member] \| Level 2 [Member] \| Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		8,015
Investments	9,319	3,583
Recurring [Member] \| Level 3 [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Investments	0	0
Fair value of financial instruments	0	0
Recurring [Member] \| Level 3 [Member] \| Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] \| Level 3 [Member] \| United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] \| Level 3 [Member] \| Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	0	0
Recurring [Member] \| Level 3 [Member] \| Municipal Bonds [Member]
Assets [Abstract]
Investments	0	0
Recurring [Member] \| Level 3 [Member] \| Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		0
Investments	$ 0	$ 0

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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- Definition

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

No definition available.

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+ References

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- References

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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