XML 43 R53.htm IDEA: XBRL DOCUMENT v3.20.1
Equity (Details)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 12 Months Ended
Nov. 30, 2015
shares
Dec. 31, 2018
USD ($)
shares
Oct. 31, 2018
USD ($)
shares
Aug. 31, 2018
shares
Feb. 28, 2018
USD ($)
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Jun. 30, 2019
$ / shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Jun. 30, 2018
$ / shares
Mar. 31, 2018
shares
Dec. 31, 2019
USD ($)
VoteperShare
Plan
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
Stock Award and Incentive Plan [Abstract]                          
Number of stock award and incentive plans | Plan                     1    
Number of shares awarded (in shares)                     700,000    
Shares available for future issuance (in shares)           1,300,000         1,300,000    
Compensation payable | $   $ 11,388       $ 20,246   $ 11,388     $ 20,246 $ 11,388  
Stock-based compensation expense | $                     $ 1,400 $ 700  
Stock Repurchase Program [Abstract]                          
Shares repurchased during the period (in shares)                     100,000 200,000  
Average price per share of repurchased shares (in dollars per share) | $ / shares                     $ 37.62 $ 37.52  
Total investment amount | $                     $ 4,100 $ 7,000  
Dividends [Abstract]                          
Dividends declared (in dollars per share) | $ / shares           $ 0.10 $ 0.10 $ 0.10 $ 0.10   $ 0.20 $ 0.20  
Total dividends declared | $                     $ 4,500 $ 4,600  
Dividends payable | $   $ 2,300       $ 2,300   $ 2,300     $ 2,300 $ 2,300  
Dividends payable, date to be paid                     Jan. 09, 2020 Jan. 09, 2019  
Maximum [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Term of RSAs and stock options                     10 years    
Class A Common Stock [Member]                          
Voting Rights [Abstract]                          
Number of votes per share | VoteperShare                     1    
Exchange Offer [Abstract]                          
Number shares tendered upon completion of exchange offer (in shares)     373,581   493,954             867,535  
Class A Common Stock [Member] | Maximum [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Shares reserved for future issuance (in shares)           2,000,000         2,000,000    
Class B Common Stock [Member]                          
Voting Rights [Abstract]                          
Number of votes per share | VoteperShare                     10    
GAMCO [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Number of GAMCO shares exchanged for each AC shares in connection with spin-off (in shares) 1                        
GAMCO [Member] | Class A Common Stock [Member]                          
Exchange Offer [Abstract]                          
Number of shares received in exchange (in shares)     1.9   1.35                
Number of shares accepted for exchange (in shares)     709,749   666,805                
Value of shares in exchange offer | $     $ 14,600   $ 17,700                
Restricted Stock Awards [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Granted (in shares) 554,100                        
Shares outstanding (in shares)   0       0   0     0 0  
Restricted Stock Awards [Member] | GAMCO [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Number of GAMCO shares exchanged for each AC shares in connection with spin-off (in shares) 554,100                        
Shares outstanding (in shares)   19,400           19,400       19,400  
Number of shares with accelerated vesting (in shares)                   19,400      
Stock compensation expense recognized due to acceleration of restrictions on RSAs | $                         $ 4,200
Phantom RSAs [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Granted (in shares)   172,800   172,800                  
Shares outstanding (in shares)   170,300       119,650   170,300     119,650 170,300  
Compensation payable | $   $ 600       $ 2,000   $ 600     $ 2,000 $ 600  
Unrecognized compensation cost | $   $ 5,400       $ 3,900   $ 5,400     $ 3,900 $ 5,400  
Weighted-average period for recognizing unrecognized compensation cost                     2 years    
Phantom RSAs [Member] | Vesting in Three Years from Date of Grant [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Awards vesting percentage                     30.00%    
Award vesting period                     3 years    
Phantom RSAs [Member] | Vesting in Five Years from Date of Grant [Member]                          
Stock Award and Incentive Plan [Abstract]                          
Awards vesting percentage                     70.00%    
Award vesting period                     5 years