XML 95 R82.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock-Based Compensation - Summary of Restricted Performance Stock Unit Activity (Detail) - PSUs [Member] - $ / shares
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Number of Awards    
Number of Awards, Beginning balance (in shares) 239,674  
Granted (in shares) 172,014  
Vested (in shares) 0  
Canceled (in shares) 0  
Number of Awards, Ending balance (in shares) 411,688 239,674
Weighted Average Grant Date Fair Value    
Weighted Average Grant Date Fair Value, Beginning balance (in dollars per share) $ 22.58  
Granted (in dollars per share) 16.85  
Vested (in dollars per share) 0  
Canceled (in dollars per share) 0  
Weighted Average Grant Date Fair Value, Ending balance (in dollars per share) $ 20.18 $ 22.58
Weighted Average Remaining Amortization Period (in Years) 2 years 6 months 7 days 1 year 8 months 12 days