Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation (Restricted Stock) (Details)

v3.8.0.1
Stock-Based Compensation (Restricted Stock) (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended
Mar. 31, 2018
USD ($)
$ / shares
shares
Unvested restricted stock units and awards  
Number of Shares  
Balance at the beginning of the period (in shares) 1,766,639
Granted (in shares) 887,757
Vested (in shares) (503,668)
Forfeited (in shares) (27,265)
Balance at the end of the period (in shares) 2,123,463
Weighted-Average Grant Date Fair Value per Share  
Balance at the beginning of the period (in dollars per share) | $ / shares $ 32.48
Granted (in dollars per share) | $ / shares 55.13
Vested (in dollars per share) | $ / shares 34.05
Forfeited (in dollars per share) | $ / shares 30.79
Balance at the end of the period (in dollars per share) | $ / shares $ 41.59
Additional disclosures  
Unrecognized compensation expense related to shares | $ $ 81,871
Unrecognized compensation expense weighted-average recognition period 2 years 4 months 24 days
Stock options  
Additional disclosures  
Unrecognized compensation expense weighted-average recognition period 1 year 7 months 6 days
Performance-based restricted stock unit awards  
Number of Shares  
Vested (in shares) (26,000)