Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS - Available-for-sale securities (Details)

v3.21.2
FAIR VALUE MEASUREMENTS - Available-for-sale securities (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Available-for-sale Securities - Amortized Cost Basis $ 35,078 $ 23,652
Available-for-sale Securities - Gross Unrealized Gains   74
Available-for-sale Securities - Gross Unrealized Losses   0
Available-for-sale Securities - Fair Value 35,051 23,726
Corporate Bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Available-for-sale Securities - Amortized Cost Basis 35,078 12,603
Available-for-sale Securities - Gross Unrealized Gains 7 74
Available-for-sale Securities - Gross Unrealized Losses (34) 0
Available-for-sale Securities - Fair Value $ 35,051 12,677
Notes Receivable [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Available-for-sale Securities - Amortized Cost Basis   5,876
Available-for-sale Securities - Gross Unrealized Gains   0
Available-for-sale Securities - Gross Unrealized Losses   0
Available-for-sale Securities - Fair Value   5,876
Preferred stock    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Available-for-sale Securities - Amortized Cost Basis   5,173
Available-for-sale Securities - Gross Unrealized Gains   0
Available-for-sale Securities - Gross Unrealized Losses   0
Available-for-sale Securities - Fair Value   $ 5,173