Members’ Equity - Fair Value Assumptions for Stock Options (Details) - Stock Options	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected volatility, minimum	73.90%	76.60%
Expected volatility, maximum	76.60%	78.20%
Risk-free interest rate, minimum (as a percent)	0.005%	0.004%
Risk-free interest rate, maximum (as a percent)	0.011%	0.005%
Expected dividend yield	0.00%	0.00%
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Average expected term (in years)	5 years 2 months 12 days	5 years 8 months 12 days
Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Average expected term (in years)	6 years 2 months 12 days	6 years