Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
2021 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	$ 8,100
2022 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	53,100
Recurring [Member]
Assets [Abstract]
Cash and cash equivalents	235,899	$ 264,325
Investments	213,813	185,621
Fair value of financial instruments	449,712	449,946
Recurring [Member] \| Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	235,899	193,312
Recurring [Member] \| United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		62,497
Investments	107,566	112,328
Recurring [Member] \| Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents		501
Investments	100,247	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		3,583
Recurring [Member] \| Level 1 [Member]
Assets [Abstract]
Cash and cash equivalents	235,899	255,809
Investments	107,566	112,328
Fair value of financial instruments	343,465	368,137
Recurring [Member] \| Level 1 [Member] \| Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	235,899	193,312
Recurring [Member] \| Level 1 [Member] \| United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents		62,497
Investments	107,566	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
Recurring [Member] \| Level 2 [Member]
Assets [Abstract]
Cash and cash equivalents	0	8,516
Investments	106,247	73,293
Fair value of financial instruments	106,247	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	100,247	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		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

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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)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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=117815213&loc=d3e19207-110258

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