XML 62 R52.htm IDEA: XBRL DOCUMENT v3.19.1
Stock-Based Compensation - Additional Information (Detail) - USD ($)
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2015
Jan. 01, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Compensation expense   $ 2,234,000 $ 1,871,000      
Fair value of options granted   $ 10.83 $ 10.43      
Excess tax benefits from stock option activity or stock-based compensation expense recognized in cash flows from operations   $ 0 $ 0      
Restricted Stock Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Restricted stock units, vested 0          
Compensation expense $ 0          
2014 Equity Incentive Plan [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of stock options that may be granted after the tenth anniversary of the 2014 Plan   0        
Annual increases in number of shares reserved for issuance as a percentage of shares of capital stock outstanding through January 1, 2024       3.00%    
Share-based compensation arrangement by share-based payment award, number of shares authorized         6,086,907 4,900,481
Options granted   957,000 596,000      
2014 Equity Incentive Plan [Member] | Share-Based Compensation Award, Tranche One [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percentage of vested shares on first anniversary of grant date   25.00%        
2014 Equity Incentive Plan [Member] | Share-based Compensation Award, Tranche Two [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period of awards granted   36 months        
2014 Equity Incentive Plan [Member] | Maximum [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Term of awards granted   10 years        
2014 Equity Incentive Plan [Member] | Maximum [Member] | Incentive Stock Options [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Share-based compensation arrangement by share-based payment award, number of shares authorized       30,000,000    
2014 Equity Incentive Plan [Member] | Employees [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period of awards granted   4 years        
2014 Equity Incentive Plan [Member] | Board of Directors [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period of awards granted   3 years        
2014 Equity Incentive Plan [Member] | Board of Directors [Member] | Subsequent Grants of Options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period of awards granted   1 year        
2014 Equity Incentive Plan [Member] | Executive Officers [Member] | Restricted Stock Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Restricted stock units, approved and granted   215,000