Fair Value Measurements (Details) - Recurring - Money market funds, US Government Securities and Agency Investments - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Estimate of fair value measurement
Fair Value Measurements
Money market funds, U.S. Government Securities and Agency Investments	$ 261,090	$ 172,119
Level 1
Fair Value Measurements
Money market funds, U.S. Government Securities and Agency Investments	$ 261,090	$ 172,119

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.

No definition available.

Name:	us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant