Stock Options And Employee Stock Purchase Plan (Stock Options) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 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	(127,838)
Number of Shares, Canceled	0
Number of Shares, Outstanding Ending of Period	659,811
Number of Shares, Exercisable	544,675
Number of Shares, Vested and expected to vest	633,034
Weighted-Average Exercise Price, Outstanding Beginning of Period	$ 24.29
Weighted-Average Exercise Price, Granted	67.35
Weighted-Average Exercise Price, Exercised	23.53
Weighted-Average Exercise Price, Canceled	0.00
Weighted-Average Exercise Price, Outstanding Ending of Period	28.49
Weighted-Average Exercise Price, Exercisable	24.08
Weighted-Average Exercise Price, Vested and expected to vest	$ 27.26
Weighted-Average Remaining Contractual Term, Outstanding (in years)	4 years 4 months 13 days
Weighted-Average Remaining Contractual Term, Exercisable (in years)	3 years 6 months 22 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	4 years 2 months 5 days
Aggregate Intrinsic Value, Outstanding	$ 26,032,294
Aggregate Intrinsic Value, Exercisable	23,891,847
Aggregate Intrinsic Value, Vested and expected to vest	25,752,888
Aggregate intrinsic values of options exercised	5,600,000	$ 12,800,000
Stock Options [Member]
Unrecognized compensation cost related to non-vested awards granted	$ 1,400,000		$ 800,000
Weighted-average period to recognize compensation cost (in years)	3 years 2 months 12 days