v3.19.3.a.u2
CONSOLIDATED STATEMENTS OF STOCKHOLDER'S EQUITY (Parenthetical)
12 Months Ended
Dec. 31, 2018
$ / shares
Class A common stock  
Cash dividend declared (in dollars per share) $ 0.20
Class A common stock | Special dividends  
Cash dividend declared (in dollars per share) 1.55
Class B common stock  
Cash dividend declared (in dollars per share) 0.20
Class B common stock | Special dividends  
Cash dividend declared (in dollars per share) $ 1.55