Stock Options And Employee Stock Purchase Plan (Stock Options) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Number of Shares, Outstanding Beginning of Period	725,649
Number of options granted	62,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 15.22
Number of Shares, Exercised	(205,621)
Number of Shares, Canceled	0
Number of Shares, Outstanding Ending of Period	582,028
Number of Shares, Exercisable	470,392
Number of Shares, Vested and expected to vest	557,548
Weighted-Average Exercise Price, Outstanding Beginning of Period	$ 24.29
Weighted-Average Exercise Price, Granted	67.35
Weighted-Average Exercise Price, Exercised	22.19
Weighted-Average Exercise Price, Canceled	0.00
Weighted-Average Exercise Price, Outstanding Ending of Period	29.62
Weighted-Average Exercise Price, Exercisable	24.77
Weighted-Average Exercise Price, Vested and expected to vest	$ 28.34
Weighted-Average Remaining Contractual Term, Outstanding (in years)	4 years 6 months 22 days
Weighted-Average Remaining Contractual Term, Exercisable (in years)	3 years 8 months 27 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	4 years 4 months 13 days
Aggregate Intrinsic Value, Outstanding	$ 24,012,309
Aggregate Intrinsic Value, Exercisable	21,687,481
Aggregate Intrinsic Value, Vested and expected to vest	23,718,233
Aggregate intrinsic values of options exercised	9,600,000	$ 14,500,000
Stock Options [Member]
Unrecognized compensation cost related to non-vested awards granted	$ 1,200,000		$ 800,000
Weighted-average period to recognize compensation cost (in years)	3 years 4 days