Stockholders' Equity - Warrants Issued to Financial Institution, Vulcan, Service Provider (Details) - USD ($)
 1 Months Ended 12 Months Ended
Aug. 29, 2013
Jun. 13, 2012
Dec. 31, 2015
Jun. 30, 2014
May. 31, 2014
Nov. 30, 2013
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Jun. 13, 2013
Convertible Preferred Stock and Stockholders' Equity                    
Amount drawn on credit facility             $ 0 $ 5,000,000 $ 5,000,000  
Warrant expense             $ (803,000) $ 9,861,000 $ 3,740,000  
Vulcan                    
Convertible Preferred Stock and Stockholders' Equity                    
Aggregate proceeds from issuance of Series A           $ 30,000,000        
Vulcan | Series A                    
Convertible Preferred Stock and Stockholders' Equity                    
Aggregate proceeds from issuance of Series A           $ 29,200,000        
Common Stock Purchase Warrants | Service Provider                    
Convertible Preferred Stock and Stockholders' Equity                    
Exercise price of warrants (in dollars per share)         $ 12.81          
Number of shares under warrant agreement (up to)     187,500   333,333          
Vesting period         4 years          
Expiration period         5 years          
Early expiration period         12 months          
Outstanding common stock warrants     145,833       145,833      
Total number of warrants earned under agreement             112,500 33,333    
Warrant expense               $ 1,700,000    
Common Stock Purchase Warrants | Service Provider | Selling and Marketing Expense                    
Convertible Preferred Stock and Stockholders' Equity                    
Reduction in warrant expense             $ 1,000,000      
Common Stock Purchase Warrants | Service Provider | Minimum                    
Convertible Preferred Stock and Stockholders' Equity                    
Expected life             1 year 4 years 4 months 24 days    
Risk-free interest rate             0.52% 1.48%    
Volatility (as a percent)             44.10% 54.80%    
Common Stock Purchase Warrants | Service Provider | Maximum                    
Convertible Preferred Stock and Stockholders' Equity                    
Expected life             4 years 5 years    
Risk-free interest rate             1.28% 1.55%    
Volatility (as a percent)             48.90% 56.80%    
Common Stock Purchase Warrants | Vulcan                    
Convertible Preferred Stock and Stockholders' Equity                    
Shares that may be purchased under warrant           666,666        
Exercise price of warrants (in dollars per share)           $ 15.00        
Expected life                 2 years  
Risk-free interest rate                 0.31%  
Volatility (as a percent)                 49.40%  
Aggregate proceeds from issuance of Series A           $ 700,000        
Common Stock Purchase Warrants | Revolving Credit Facility                    
Convertible Preferred Stock and Stockholders' Equity                    
Shares that may be purchased under warrant 66,666 26,666                
Exercise price of warrants (in dollars per share) $ 7.92 $ 11.51               $ 7.92
Advances in aggregate principal amount (greater than)   $ 4,000,000.0                
Amount drawn on credit facility $ 5,000,000                  
Expected life                 10 years  
Risk-free interest rate                 2.78%  
Volatility (as a percent)                 64.80%  
Number of shares exercised through a net settlement       66,666            
Shares issued for exercise of warrants       27,526            
Scenario Representing Advances On Credit Facility Of Specified Amount [Member] | Common Stock Purchase Warrants | Revolving Credit Facility                    
Convertible Preferred Stock and Stockholders' Equity                    
Shares that may be purchased under warrant   66,666