XML 41 R31.htm IDEA: XBRL DOCUMENT v3.22.1
Revenues - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Disaggregation of Revenue [Line Items]    
Contract with customer, liability, revenue recognized $ 30,900 $ 29,500
Accounts receivable, net $ 2,068  
Accounts receivable, net, percent 12.00%  
Contract assets $ (561)  
Contract assets, percent (4.00%)  
Deferred revenue $ 25,315  
Deferred revenue, percent 72.00%  
Textbook Library    
Disaggregation of Revenue [Line Items]    
Operating lease income $ 4,800 $ 10,700