XML 52 R38.htm IDEA: XBRL DOCUMENT v3.10.0.1
Share-based Compensation - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Apr. 30, 2018
Mar. 31, 2018
Stock Option Awards            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock option awards granted 103,000          
Options outstanding, shares 1,481,000   1,481,000     1,463,000
2013 Equity Plan | Stock Option Awards            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options vested 157,500          
Aggregate fair value of stock option vested $ 8,900,000          
Weighted average grant date fair value of stock option awards $ 50.76 $ 72.78        
Share-based compensation expense recognized $ 3,400,000 $ 3,800,000 $ 8,100,000 $ 6,900,000    
Unrecognized share-based compensation expense 37,600,000   $ 37,600,000      
Unrecognized compensation expense expected to be recognized     3 years 3 months 18 days      
2013 Equity Plan | Other Stock-based Awards            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Share-based compensation expense recognized $ 0   $ 0      
Unrecognized compensation expense expected to be recognized     3 years 10 months 24 days      
Vesting period 4 years          
Unrecognized share-based compensation expense $ 500,000   $ 500,000      
2013 Equity Plan | Class A | Other Stock-based Awards            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Other stock-based awards granted 10,000          
Other stock-based awards granted weighted average exercise price per award $ 129.90          
2013 Equity Plan | Class A | Board of Directors            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Share-based compensation, stock authorized 2,300,000   2,300,000   1,700,000  
2013 Equity Plan | Class A | Employees, Officers, and Directors | Stock Option Awards            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares of class A common stock reserved and available for future issuance 565,000   565,000      
Stock option awards granted 102,500          
Options outstanding, shares 1,481,233   1,481,233