Compensation Plans  Valuation Assumptions (Details)  Stock options  Class A common stock 
12 Months Ended  

Dec. 31, 2021 
Dec. 31, 2020 

Expected volatility, minimum  100.00%  96.00% 
Expected volatility, maximum  107.00%  103.00% 
Expected dividend yield  0.00%  0.00% 
Riskfree interest rate, minimum  0.78%  0.23% 
Riskfree interest rate, maximum  1.37%  1.72% 
Minimum  
Expected term  5 years 3 months  5 years 1 month 24 days 
Maximum  
Expected term  6 years 3 months  6 years 3 months 
X  
 Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://fasb.org/usgaap/role/ref/legacyRef

X  
 Definition The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probabilityweighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. No definition available.

X  
 Definition The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probabilityweighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. No definition available.

X  
 Definition The maximum riskfree interest rate assumption that is used in valuing an option on its own shares. No definition available.

X  
 Definition The minimum riskfree interest rate assumption that is used in valuing an option on its own shares. No definition available.

X  
 Definition Expected term of award under sharebased payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Reference 1: http://fasb.org/usgaap/role/ref/legacyRef

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