Annual report pursuant to Section 13 and 15(d)

Assets and Liabilities Measured at Fair Value (Details)

v3.10.0.1
Assets and Liabilities Measured at Fair Value (Details) - USD ($)
 12 Months Ended
Oct. 03, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Recurring          
Assets and Liabilities Measured at Fair Value          
Cash equivalents     $ 67,329,000 $ 76,304,000  
Level 1 | Recurring          
Assets and Liabilities Measured at Fair Value          
Cash equivalents     $ 67,329,000 $ 76,304,000  
Series C common stock | Zero-strike call option | Call Option          
Assets and Liabilities Measured at Fair Value          
Derivative underlying share amount 527,156   0 0 704,908
Derivative premium paid $ 47,700,000   $ 142,800,000 $ 149,400,000 $ 47,900,000
Derivative settlement proceeds   $ 50,000,000 $ 146,500,000 $ 155,700,000