Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation (Summary of Restricted Stock Unit Activity) (Details)

v3.6.0.2
Stock-Based Compensation (Summary of Restricted Stock Unit Activity) (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock units outstanding, beginning, number of shares 553,289 658,760 674,494
Granted, number of shares 205,734 207,040 272,642
Vested, number of shares (235,059) (243,765) (220,348)
Forfeited, number of shares (57,489) (68,746) (68,028)
Restricted stock units outstanding, ending, number of shares 466,475 553,289 658,760
Restricted stock units outstanding, beginning, weighted average grate date fair value per share $ 38.85 $ 31.03 $ 25.67
Granted, weighted average grant date fair value per share 55.93 51.07 38.98
Vested, weighted average grant date fair value 33.98 28.09 25.21
Forfeited, weighted average grant date fair value 46.35 34.57 28.51
Restricted stock units outstanding, ending, weighted average grate date fair value per share $ 47.23 $ 38.85 $ 31.03