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Revenue - Narrative (Details) - USD ($)
Mar. 31, 2022
Dec. 31, 2021
Disaggregation of Revenue [Line Items]    
Contract assets $ 0 $ 0
Deferred revenue 27,920,000 21,776,000
Courses in Progress    
Disaggregation of Revenue [Line Items]    
Future revenue 10,700,000 12,900,000
Future Courses    
Disaggregation of Revenue [Line Items]    
Future revenue $ 17,200,000 $ 8,900,000