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Stockholders' Equity (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Vote
$ / shares
Dec. 31, 2016
$ / shares
Dec. 31, 2018
USD ($)
Vote
$ / shares
Dec. 31, 2017
USD ($)
$ / shares
Dec. 31, 2016
USD ($)
$ / shares
Common Stock [Member]          
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]          
Common stock dividend paid in cash (in dollars per share) | $ / shares $ 1.00        
Aggregate dividends paid on common Stock | $     $ 32,595 $ 10,473 $ 27,674
Class A Common Stock [Member]          
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]          
Percentage of number of directors elected under stock voting right     75.00%    
Number of votes per share | Vote 10   10    
Conversion basis     1-for-1 basis    
Common stock dividend paid in cash (in dollars per share) | $ / shares   $ 0.95 $ 1.63 $ 0.51 $ 1.365
Aggregate dividends paid on common Stock | $     $ 2,869 $ 919 $ 2,735
Class A Common Stock [Member] | Minimum [Member]          
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]          
Preferential dividend rate of common stock of dividends paid 105.00%   105.00%