Quarterly report pursuant to Section 13 or 15(d)

Revenue Recognition - Effect of Adoption of 2014-09 on Financial Statements (Details)

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Revenue Recognition - Effect of Adoption of 2014-09 on Financial Statements (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Jan. 01, 2018
Dec. 31, 2017
Revenue        
Revenue from contract with customer $ 201,301 $ 152,919    
Operating expenses:        
Sales and marketing 50,241 35,147    
Net income 10,901 8,195    
Assets        
Accounts receivable, less allowance for doubtful accounts 101,005   $ 116,580 $ 124,505
Other current assets 9,838   9,393 6,622
Other assets 19,533   15,469 11,010
Liabilities        
Current portion of deferred revenue 109,965      
Deferred revenue 5,457      
Adjustments due to ASU 2014-09        
Operating expenses:        
Net income 10,901      
Balances without adoption of ASU 2014-09        
Assets        
Accounts receivable, less allowance for doubtful accounts       124,505
Other current assets       6,622
Other assets       $ 11,010
Balances without adoption of ASU 2014-09 | Adjustments due to ASU 2014-09        
Revenue        
Revenue from contract with customer 200,874      
Operating expenses:        
Sales and marketing 52,101      
Net income 8,614      
Assets        
Accounts receivable, less allowance for doubtful accounts 109,266      
Other current assets 6,201      
Other assets 14,114      
Liabilities        
Current portion of deferred revenue 110,305      
Deferred revenue 5,457      
Effect of Change on Net Income Higher/(Lower) | Adjustments due to ASU 2014-09        
Revenue        
Revenue from contract with customer 427      
Operating expenses:        
Sales and marketing 1,860      
Net income 2,287      
Assets        
Accounts receivable, less allowance for doubtful accounts (8,261)   (7,925)  
Other current assets 3,637   2,771  
Other assets 5,419   $ 4,459  
Liabilities        
Current portion of deferred revenue (340)      
Deferred revenue 0      
On demand        
Revenue        
Revenue from contract with customer 193,300 $ 146,213    
On demand | Balances without adoption of ASU 2014-09 | Adjustments due to ASU 2014-09        
Revenue        
Revenue from contract with customer 193,455      
On demand | Effect of Change on Net Income Higher/(Lower) | Adjustments due to ASU 2014-09        
Revenue        
Revenue from contract with customer (155)      
Professional and other        
Revenue        
Revenue from contract with customer 8,001      
Professional and other | Balances without adoption of ASU 2014-09 | Adjustments due to ASU 2014-09        
Revenue        
Revenue from contract with customer 7,419      
Professional and other | Effect of Change on Net Income Higher/(Lower) | Adjustments due to ASU 2014-09        
Revenue        
Revenue from contract with customer $ 582