XML 71 R61.htm IDEA: XBRL DOCUMENT v3.21.1
Share Capital - Changes in Number of Shares of Class A Stock Outstanding (Details) - Class A Stock - shares
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]    
Class A Stock outstanding, beginning of period 12,381,778 12,698,703
Issued pursuant to shared-based compensation plans 204,265 321,541
Repurchased and canceled pursuant to the stock buy-back 0 409,504
Class A Stock outstanding, end of period 12,586,043 12,610,740