CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' (DEFICIT) EQUITY [Parenthetical] - shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	63,190
Convertible Shares, Common Stock Class A to Common Stock Class D [Member]
Conversion of Stock, Shares Converted		51,467
Common Stock Class A [Member]
Stock Repurchased During Period, Shares	4,160
Common Stock Class D [Member]
Stock Repurchased During Period, Shares	3,989,822	2,408,198

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

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