CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - shares	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	15,000	58,190
Common Stock Class A [Member]
Stock Repurchased During Period, Shares	54,896	4,160
Common Stock Class D [Member]
Stock Repurchased During Period, Shares	2,588,796	3,062,574
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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