v3.6.0.2
SUBSEQUENT EVENTS (Details) - $ / shares
1 Months Ended 4 Months Ended 9 Months Ended 12 Months Ended
Mar. 17, 2017
Jan. 11, 2017
Jan. 05, 2017
Jan. 04, 2017
Jan. 31, 2017
Nov. 30, 2014
Apr. 30, 2014
Apr. 21, 2014
Dec. 31, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 13, 2016
Subsequent events                          
Special dividend declared (in dollars per share)                         $ 1.25
Subsequent event                          
Subsequent events                          
Dividends declared per share       $ 0.37                  
Dividend paid (in dollars per share) $ 0.37                        
Class A common stock                          
Subsequent events                          
Dividends declared per share                   $ 3.29 $ 1.00 $ 1.4  
Shares issued (in shares)                 7,483,442        
Common stock, shares outstanding           19,770,893       20,561,108 20,273,118    
Remaining shares sold                   20,948,998 20,536,740    
Class A common stock | Subsequent event                          
Subsequent events                          
Dividend paid (in dollars per share)     $ 1.25                    
Shares issued (in shares)   5,750,000                      
Increase in the number of common shares outstanding   5,356,876                      
Remaining shares sold   393,124                      
Class B common stock                          
Subsequent events                          
Shares issued (in shares)             36,158,698 36,158,698          
Common stock, shares outstanding                   31,138,193 31,229,236    
Remaining shares sold                   31,138,193 31,229,236    
Follow-on Offering | Class A common stock                          
Subsequent events                          
Shares issued (in shares)   5,750,000       4,509,400              
Follow-on Offering | Class B common stock                          
Subsequent events                          
Number of shares repurchased and retired         5,356,876 1,509,131              
Price per share of stock which was repurchased and retired         $ 101 $ 28              
Follow-on Offering | Class B common stock | Subsequent event                          
Subsequent events                          
Number of shares repurchased and retired   5,356,876                      
Price per share of stock which was repurchased and retired   $ 101