Shareholders' Equity and Common Stock Equivalents - Stock Option Information by Ranges of Exercise Prices (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Options (in shares)	774,821	719,015	747,032
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 36.65	$ 32.80
Total Outstanding Options, Weighted Average Remaining Term	7 years 6 months
Vested and Exercisable Options (in shares)	271,116	258,321
Vested and Exercisable Options, Weighted Average Option Price per Share (in usd per share)	$ 31.42	$ 27.12	$ 22.73
Vested and Exercisable Options, Weighted Average Remaining Term	5 years 11 months 23 days
Minimum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 41.95
Maximum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 44.75
Range One
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Options (in shares)	36,524
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 19.77
Total Outstanding Options, Weighted Average Remaining Term	9 months 25 days
Vested and Exercisable Options (in shares)	36,524
Vested and Exercisable Options, Weighted Average Option Price per Share (in usd per share)	$ 19.77
Vested and Exercisable Options, Weighted Average Remaining Term	9 months 25 days
Range One | Minimum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 17.01
Range One | Maximum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 22.69
Range Two
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Options (in shares)	320,897
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 31.01
Total Outstanding Options, Weighted Average Remaining Term	6 years 8 months 5 days
Vested and Exercisable Options (in shares)	183,685
Vested and Exercisable Options, Weighted Average Option Price per Share (in usd per share)	$ 30.85
Vested and Exercisable Options, Weighted Average Remaining Term	6 years 4 months 24 days
Range Two | Minimum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 28.88
Range Two | Maximum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 33.41
Range Three
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Options (in shares)	199,452
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 41.82
Total Outstanding Options, Weighted Average Remaining Term	8 years 2 months 8 days
Vested and Exercisable Options (in shares)	50,907
Vested and Exercisable Options, Weighted Average Option Price per Share (in usd per share)	$ 41.82
Vested and Exercisable Options, Weighted Average Remaining Term	8 years 2 months 8 days
Range Three | Minimum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 38.05
Range Three | Maximum
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 41.95
Range Four
Summary of options outstanding segregated by ranges of exercise prices
Total Outstanding Options, Options (in shares)	217,948
Total Outstanding Options, Weighted Average Option Price per Share (in usd per share)	$ 43.05
Total Outstanding Options, Weighted Average Remaining Term	9 years 2 months 8 days
Vested and Exercisable Options (in shares)	0
Vested and Exercisable Options, Weighted Average Option Price per Share (in usd per share)	$ 0
Vested and Exercisable Options, Weighted Average Remaining Term	0 years