Stock Options And Employee Stock Purchase Plan (Stock Options) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Number of Shares, Outstanding Beginning of Period	375,675
Number of options granted	400,000
Number of Shares, Exercised	(27,679)
Number of Shares, Canceled	0
Number of Shares, Outstanding Ending of Period	747,996
Number of Shares, Exercisable	334,196
Number of Shares, Vested and expected to vest	601,462
Weighted-Average Exercise Price, Outstanding Beginning of Period	$ 31.30
Weighted-Average Exercise Price, Granted	75.03
Weighted-Average Exercise Price, Exercised	21.45
Weighted-Average Exercise Price, Canceled	0.00
Weighted-Average Exercise Price, Outstanding Ending of Period	55.05
Weighted-Average Exercise Price, Exercisable	30.62
Weighted-Average Exercise Price, Vested and expected to vest	$ 50.20
Weighted-Average Remaining Contractual Term, Outstanding (in years)	6 years 3 months 22 days
Weighted-Average Remaining Contractual Term, Exercisable (in years)	2 years 2 months 12 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	5 years 5 months 19 days
Aggregate Intrinsic Value, Outstanding	$ 17,856,319
Aggregate Intrinsic Value, Exercisable	16,140,653
Aggregate Intrinsic Value, Vested and expected to vest	17,274,251
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	1,500,000	$ 1,300,000
Allocated Share-based Compensation Expense	$ 6,420,000	$ 3,614,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Estimated Forfeiture Rate	10.74%	15.31%
Employee Stock Option [Member]
Allocated Share-based Compensation Expense	$ 232,000	$ 100,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	7 years 6 months 26 days