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CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares
3 Months Ended 12 Months Ended
Dec. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Class A Common Stock [Member]        
Treasury stock (in shares) 522,410 522,410 522,410 522,410
Cash dividends, common stock (in dollars per share) $ 0.95 $ 1.63 $ 0.51 $ 1.365
Common Stock [Member]        
Cash dividends, common stock (in dollars per share)   $ 1.72 $ 0.54 $ 1.44