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

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

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