XML 57 R35.htm IDEA: XBRL DOCUMENT v3.10.0.1
Summary of Significant Accounting Policies - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2018
USD ($)
Segment
$ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Dec. 31, 2016
USD ($)
$ / shares
shares
Sep. 30, 2017
USD ($)
May 24, 2016
USD ($)
Summary Of Significant Accounting Policies [Line Items]          
Letter of credit, amount     $ 500    
Long-term marketable securities, minimum original maturity term     1 year    
Investment fund $ 0 $ 0      
Gain (loss) on investments 0 0 $ 0    
Fair value of other assets 0 0      
Fair value of other liabilities $ 0 $ 0      
Stock options, outstanding | shares 998,226 734,940      
Stock options, weighted average exercise price | $ / shares $ 27.54 $ 20.80      
Common stock excluded from calculation of diluted earnings per share | shares 479,854 317,923 381,686    
Number of operating segment | Segment 1        
Number of reporting segment | Segment 2        
Goodwill impairment $ 0 $ 0 $ 0    
New accounting pronouncement, cumulative effect of change on cash, cash equivalents and restricted cash (677,000)        
Advertising Expense 200,000 200,000 400,000    
Deferred Rent Credit 4,000,000        
Cash and Cash Equivalents, at Carrying Value 193,822,000 173,759,000 122,233,000    
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Cash and Cash Equivalents, at Carrying Value $ 126,600,000        
ASU No. 2016-18 | Cash, Cash Equivalents and Restricted Cash          
Summary Of Significant Accounting Policies [Line Items]          
New accounting pronouncement, cumulative effect of change on cash, cash equivalents and restricted cash     $ 450,000 $ 450,000  
2.125% Convertible Senior Notes due 2021          
Summary Of Significant Accounting Policies [Line Items]          
Principal amount   11,000     $ 115,000,000
Notes, due date Jun. 01, 2021        
Notes, frequency of periodic payment Semi-annually        
Notes, date of first required payment Dec. 01, 2016        
Total convertible senior notes $ 103,488,000 $ 99,250,000      
Fair value of convertible senior notes 184,600,000        
Minimum          
Summary Of Significant Accounting Policies [Line Items]          
Short-term marketable securities, minimum original maturity term     90 days    
Operating Lease Right Of Use Asset 12,000,000        
Lease Liability 16,000,000        
Maximum [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Operating Lease Right Of Use Asset 14,000,000        
Lease Liability $ 18,000,000        
Option To Purchase Common Stock          
Summary Of Significant Accounting Policies [Line Items]          
Stock options, outstanding | shares 998,226 734,940 1,236,586    
Stock options, weighted average exercise price | $ / shares $ 27.54 $ 20.80 $ 12.05    
Restricted Stock Units (RSUs)          
Summary Of Significant Accounting Policies [Line Items]          
Restricted stock units, outstanding | shares 705,413 505,235      
Restricted Stock Units (RSUs) | Awards Granted to Non-Executive Level Employees          
Summary Of Significant Accounting Policies [Line Items]          
Estimated forfeiture rates 8.00%        
Restricted Stock Units (RSUs) | Awards Granted to Executive Level Employees          
Summary Of Significant Accounting Policies [Line Items]          
Estimated forfeiture rates 3.00%        
Employee Stock Option | Awards Granted to Non-Executive Level Employees          
Summary Of Significant Accounting Policies [Line Items]          
Estimated forfeiture rates 8.00%        
Employee Stock Option | Awards Granted to Executive Level Employees          
Summary Of Significant Accounting Policies [Line Items]          
Estimated forfeiture rates 3.00%        
Non-Employee Directors          
Summary Of Significant Accounting Policies [Line Items]          
Estimated forfeiture rates 0.00%