Annual report pursuant to Section 13 and 15(d)

Debt Instruments - Narrative (Details)

v3.6.0.2
Debt Instruments - Narrative (Details)
$ / shares in Units, shares in Millions
1 Months Ended 12 Months Ended
Dec. 09, 2015
USD ($)
day
$ / shares
$ / unit
shares
Sep. 30, 2016
USD ($)
Dec. 31, 2015
USD ($)
May 31, 2011
USD ($)
Dec. 31, 2016
USD ($)
$ / shares
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Debt Instruments              
Payments for capped call transactions         $ 0 $ 43,160,000 $ 0
Debt instrument, conversion price (in dollars per share) | $ / shares $ 16.42            
Share price (in dollars per share) | $ / shares         $ 13.04    
Line of credit              
Debt Instruments              
Interest rate (percent)   3.81%          
Maximum borrowings available     $ 120,000,000.0     120,000,000.0  
Credit facility financial covenant, minimum liquidity     10,000,000.0 $ 5,000,000.0      
Line of credit facility, unused capacity, commitment fee percentage       0.375%      
Borrowings from credit facility   $ 90,000,000.0          
Credit facility     0   $ 90,000,000 0  
Available borrowing capacity     118,900,000   $ 28,800,000 118,900,000  
Debt issuance cost     400,000     400,000  
Credit facility term remaining         2 years    
Amortization of debt issuance costs         $ 400,000 200,000 $ 200,000
Line of credit | Minimum              
Debt Instruments              
Interest rate (percent)         2.00%    
Line of credit | Maximum              
Debt Instruments              
Interest rate (percent)         2.25%    
Line of credit | Alternate base rate | Minimum              
Debt Instruments              
Margin       1.00%      
Line of credit | Alternate base rate | Maximum              
Debt Instruments              
Margin       1.25%      
Line of credit | LIBOR | Minimum              
Debt Instruments              
Margin       2.00%      
Line of credit | LIBOR | Maximum              
Debt Instruments              
Margin       2.25%      
Letter of credit              
Debt Instruments              
Maximum borrowings available         $ 15,000,000.0    
Outstanding amount     $ 1,100,000   $ 1,200,000 $ 1,100,000  
Convertible debt | Notes              
Debt Instruments              
Aggregate principal amount $ 345,000,000.0            
Interest rate (percent) 1.75%       1.75%    
Net proceeds from sale of debt $ 336,500,000            
Payments for capped call transactions $ 43,200,000            
Debt instrument, conversion ratio 0.060905            
Debt instrument, conversion price (in dollars per share) | $ / shares $ 16.42            
Debt instrument, redemption price, percentage of principal 100.00%            
Debt conversion, maximum number of shares of common stock convertible by notes (shares) | shares 27.3            
Value of debt $ 233,500,000       $ 357,200,000    
Carrying amount of equity component reported in additional paid-in-capital 103,000,000.0            
Debt fees and expenses $ 2,600,000            
Initial cap price (in dollars per share) | $ / unit 25.26            
Convertible debt | Notes | Redemption, period 1              
Debt Instruments              
Debt instrument, threshold percentage of stock price trigger 130.00%            
Debt instrument, threshold trading days | day 20            
Debt instrument, threshold consecutive trading days 30 days            
Debt instrument, threshold notice trading days | day 5            
Convertible debt | Notes | Redemption, period 2              
Debt Instruments              
Debt instrument, threshold percentage of stock price trigger 130.00%            
Debt instrument, threshold trading days | day 20            
Debt instrument, threshold consecutive trading days 30 days            
Convertible debt | Notes | Redemption, period 3              
Debt Instruments              
Debt instrument, threshold note trading days | day 5            
Debt instrument, threshold principle amount of note trigger $ 1,000            
Debt instrument, threshold consecutive note trading days 10 days            
Debt instrument, threshold percentage of note price trigger 98.00%