Quarterly report pursuant to Section 13 or 15(d)

Assets and Liabilities Measured at Fair Value (Details)

v3.8.0.1
Assets and Liabilities Measured at Fair Value (Details) - USD ($)
$ in Thousands
 1 Months Ended
Oct. 03, 2017
Sep. 30, 2017
Dec. 31, 2016
Aug. 31, 2017
Apr. 30, 2017
Mar. 31, 2017
Level 2 input            
Volatility   21.10%        
Interest rate   1.30%        
Dividend yield   0.00%        
Zero-strike call option            
Assets and Liabilities Measured at Fair Value            
Derivative premium paid $ 47,700          
Derivative settlement proceeds       $ 53,800   $ 50,000
Zero-strike call option | Call Option            
Assets and Liabilities Measured at Fair Value            
Derivative underlying share amount 527,156   704,908   600,242  
Derivative premium paid     $ (47,900)   $ (50,000)  
Total            
Assets and Liabilities Measured at Fair Value            
Derivative Asset     49,019      
Total | Recurring            
Assets and Liabilities Measured at Fair Value            
Cash equivalents   $ 134,574 198,011      
Quoted prices in active markets for identical assets (Level 1) | Recurring            
Assets and Liabilities Measured at Fair Value            
Cash equivalents   $ 134,574 198,011      
Significant other observable inputs (Level 2)            
Assets and Liabilities Measured at Fair Value            
Derivative Asset     $ 49,019