Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - Stock Options (Details)

v3.10.0.1
Equity-Based Compensation - Stock Options (Details) - Stock options - USD ($)
$ / shares in Units, $ in Millions
6 Months Ended 12 Months Ended
Jun. 30, 2018
Dec. 31, 2017
Stock options    
Outstanding at the beginning of the period (in shares) 660,512  
Options forfeited (in shares) (24,293)  
Outstanding at the end of the period (in shares) 636,219 660,512
Vested or expected to vest (in shares) 636,219  
Exercisable (in shares) 502,589  
Weighted average exercise price    
Outstanding at the beginning of the period (in dollars per share) $ 50.48  
Options forfeited (in dollars per share) 50.00  
Outstanding at the end of the period (in dollars per share) 50.50 $ 50.48
Vested or expected to vest (in dollars per share) 50.50  
Exercisable (in dollars per share) $ 50.63  
Weighted average remaining contractual life    
Outstanding 6 years 4 months 24 days 7 years 22 days
Vested or expected to vest 6 years 4 months 24 days  
Exercisable 6 years 3 months 18 days  
Additional disclosures    
Unrecognized stock-based compensation expense $ 1.6  
Weighted average period for recognizing unrecognized stock-based compensation expense 9 months 18 days  
Maximum    
Stock-based compensation    
Contractual life 10 years