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Fair Value Measurements - Fair value hierarchy of assets and liabilities (Details) - Fair Value, Measurements, Recurring - USD ($)
$ in Thousands
Mar. 31, 2022
Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds $ 37,862 $ 37,861
Equity securities 105,675 47,878
NAV Practical Expedient (No Fair Value Level)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds 0 0
Equity securities 9,533 9,975
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds 37,862 37,861
Equity securities 96,142 37,903
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds 0 0
Equity securities 0 0
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds 0 0
Equity securities $ 0 $ 0