Stock Plans and Stock Based Compensation - Options and SARs Outstanding and Exercisable (Details)
|
12 Months Ended |
|
Dec. 31, 2017
$ / shares
shares
|
|---|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Outstanding (in shares) | shares |
269,506
|
| Weighted average remaining contractual life (in years) |
5 years 3 months 26 days
|
| Weighted average exercise price (in dollars per share) |
$ 47.34
|
| Number exercisable (in shares) | shares |
130,610
|
| Weighted average exercise price (in dollars per share) |
$ 41.88
|
| $20.01-29.30 |
|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Range of exercise prices, lower range (in dollars per share) |
20.01
|
| Range of exercise prices, upper range (in dollars per share) |
$ 29.30
|
| Outstanding (in shares) | shares |
1,734
|
| Weighted average remaining contractual life (in years) |
3 years 5 months 5 days
|
| Weighted average exercise price (in dollars per share) |
$ 21.65
|
| Number exercisable (in shares) | shares |
1,734
|
| Weighted average exercise price (in dollars per share) |
$ 21.65
|
| $29.31-35.70 |
|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Range of exercise prices, lower range (in dollars per share) |
29.31
|
| Range of exercise prices, upper range (in dollars per share) |
$ 35.70
|
| Outstanding (in shares) | shares |
626
|
| Weighted average remaining contractual life (in years) |
11 months 16 days
|
| Weighted average exercise price (in dollars per share) |
$ 30.96
|
| Number exercisable (in shares) | shares |
626
|
| Weighted average exercise price (in dollars per share) |
$ 30.96
|
| $35.71-37.50 |
|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Range of exercise prices, lower range (in dollars per share) |
35.71
|
| Range of exercise prices, upper range (in dollars per share) |
$ 37.50
|
| Outstanding (in shares) | shares |
48,855
|
| Weighted average remaining contractual life (in years) |
3 years 7 months 7 days
|
| Weighted average exercise price (in dollars per share) |
$ 37.00
|
| Number exercisable (in shares) | shares |
35,826
|
| Weighted average exercise price (in dollars per share) |
$ 37.00
|
| $37.51-41.00 |
|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Range of exercise prices, lower range (in dollars per share) |
37.51
|
| Range of exercise prices, upper range (in dollars per share) |
$ 41.00
|
| Outstanding (in shares) | shares |
38,447
|
| Weighted average remaining contractual life (in years) |
5 years 3 months 8 days
|
| Weighted average exercise price (in dollars per share) |
$ 40.60
|
| Number exercisable (in shares) | shares |
15,248
|
| Weighted average exercise price (in dollars per share) |
$ 40.60
|
| $41.01-50.00 |
|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Range of exercise prices, lower range (in dollars per share) |
41.01
|
| Range of exercise prices, upper range (in dollars per share) |
$ 50.00
|
| Outstanding (in shares) | shares |
115,236
|
| Weighted average remaining contractual life (in years) |
4 years 6 months 26 days
|
| Weighted average exercise price (in dollars per share) |
$ 45.92
|
| Number exercisable (in shares) | shares |
70,058
|
| Weighted average exercise price (in dollars per share) |
$ 43.79
|
| $50.01-60.00 |
|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Range of exercise prices, lower range (in dollars per share) |
50.01
|
| Range of exercise prices, upper range (in dollars per share) |
$ 60.00
|
| Outstanding (in shares) | shares |
45,117
|
| Weighted average remaining contractual life (in years) |
7 years 9 months 15 days
|
| Weighted average exercise price (in dollars per share) |
$ 56.29
|
| Number exercisable (in shares) | shares |
7,118
|
| Weighted average exercise price (in dollars per share) |
$ 56.29
|
| $60.01-86.18 |
|
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |
|
| Range of exercise prices, lower range (in dollars per share) |
60.01
|
| Range of exercise prices, upper range (in dollars per share) |
$ 86.18
|
| Outstanding (in shares) | shares |
19,491
|
| Weighted average remaining contractual life (in years) |
8 years 9 months 15 days
|
| Weighted average exercise price (in dollars per share) |
$ 77.01
|
| Number exercisable (in shares) | shares |
0
|
| Weighted average exercise price (in dollars per share) |
|