CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - shares	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		15,000
Common Stock Class A [Member]
Stock Repurchased During Period, Shares		22,380
Class D common stock
Stock Repurchased During Period, Shares	547,801	1,220,657
Stock Issued During Period, Shares, New Issues		755,239

Number of share options (or share units) exercised during the current period.

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