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Common Stock and Stock-Based Compensation Plans - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of purchase rights granted under 2002 employee stock purchase plan 0 0  
2011 Stock Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options and stock appreciation rights granted under stock incentive plans vesting rate, year one 25.00%   25.00%
Remaining shares vesting period     36 months
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares vesting period     4 years
Stock Appreciation Rights (SARs) | Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options granted percentage 400.00%   400.00%
Restricted Stock Units (RSUs)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation expense $ 14,342   $ 14,342
Unrecognized compensation expense, weighted-average period of recognition     1 year 7 months 6 days
Employees and non-employees award vesting, description     RSUs granted to employees generally vest in three equal annual installments starting on the first anniversary of the grant date. RSUs granted to non-employee directors generally vest in full on the first anniversary of the grant date.
Stock Options, SARs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation expense $ 308   $ 308
Unrecognized compensation expense, weighted-average period of recognition     1 year 2 months 12 days
Non Employee Director      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options granted under stock incentive plan vesting rate, each anniversary 25.00%   25.00%
Employee | Restricted Stock Units (RSUs)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares vesting period     3 years
Non-Employee | Restricted Stock Units (RSUs)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares vesting period     1 year