Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation (Restricted Stock) (Details)

v3.10.0.1
Stock-Based Compensation (Restricted Stock) (Details) - Unvested restricted stock units and awards - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Sep. 30, 2018
Number of Shares        
Balance at the beginning of the period (in shares) 1,880,744 2,161,347 1,766,639 1,766,639
Granted (in shares) 58,359   925,641  
Vested (in shares) (159,783) (253,279) (503,668)  
Forfeited (in shares) (31,828) (27,324) (27,265)  
Balance at the end of the period (in shares) 1,747,492 1,880,744 2,161,347 1,747,492
Weighted-Average Grant Date Fair Value per Share        
Balance at the beginning of the period (in dollars per share) $ 43.36 $ 41.59 $ 32.48 $ 32.48
Granted (in dollars per share) 58.51   55.21  
Vested (in dollars per share) 31.23 31.13 34.05  
Forfeited (in dollars per share) 44.25 39.78 30.79  
Balance at the end of the period (in dollars per share) $ 44.98 $ 43.36 $ 41.59 $ 44.98
Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract]        
Unrecognized compensation expense related to shares $ 65,884     $ 65,884
Unrecognized compensation expense weighted-average recognition period       2 years