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Fair Value Measurements - Additional Information (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Feb. 29, 2016
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Fair Value Disclosures [Line Items]            
Transfers from Level 1 to Level 3       $ 0   $ 0
Transfers from Level 3 to Level 1       0   $ 0
Available sale of securities gross realized gains   $ 82,000   286,000    
Available sale of securities gross realized losses   14,000   55,000    
Remeasurement of fair-value contingent consideration       $ (2,790,000) $ 3,745,000  
8.2% Senior Convertible Notes Due 2022            
Fair Value Disclosures [Line Items]            
Aggregate principal amount $ 100,000,000          
Convertible notes, interest rate 8.20%          
Debt instrument maturity date Mar. 31, 2022          
Fair value assumptions, expected volatility rate       55.00%    
Other Expense, Net            
Fair Value Disclosures [Line Items]            
Remeasurement of fair-value contingent consideration   300,000 $ (1,600,000) $ (2,800,000) $ 3,700,000  
Level 3 | 8.2% Senior Convertible Notes Due 2022            
Fair Value Disclosures [Line Items]            
Debt instrument fair value   $ 107,000,000   $ 107,000,000    
Level 3 | Long-Term Debt | Straight Debt            
Fair Value Disclosures [Line Items]            
Discount rate       15.20%    
Fair Value Measurements Recurring Basis | Level 3 | Contingent Consideration            
Fair Value Disclosures [Line Items]            
Discount rate       25.00%    
Counterparty credit risk given the cash payment       8.00%    
Increase (decrease) in expected probability of compound transaction payment occurrence       1.00%    
Estimated fair value fluctuation of Compound Transaction Payment       $ 100,000    
Maximum            
Fair Value Disclosures [Line Items]            
Available sale of securities remaining contractual period       1 year