Stock Options And Employee Stock Purchase Plan (Stock Options) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Number of Shares, Outstanding Beginning of Period	566,428
Number of options granted	0
Number of Shares, Exercised	(51,458)
Number of Shares, Canceled	(9,700)
Number of Shares, Outstanding Ending of Period	505,270
Number of Shares, Exercisable	409,655
Number of Shares, Vested and expected to vest	486,871
Weighted-Average Exercise Price, Outstanding Beginning of Period	$ 29.74
Weighted-Average Exercise Price, Granted	0.00
Weighted-Average Exercise Price, Exercised	25.51
Weighted-Average Exercise Price, Canceled	26.92
Weighted-Average Exercise Price, Outstanding Ending of Period	30.23
Weighted-Average Exercise Price, Exercisable	24.76
Weighted-Average Exercise Price, Vested and expected to vest	$ 29.01
Weighted-Average Remaining Contractual Term, Outstanding (in years)	4 years 2 months 1 day
Weighted-Average Remaining Contractual Term, Exercisable (in years)	3 years 3 months 18 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	4 years
Aggregate Intrinsic Value, Outstanding	$ 16,199,622
Aggregate Intrinsic Value, Exercisable	15,082,140
Aggregate Intrinsic Value, Vested and expected to vest	16,123,590
Aggregate intrinsic values of options exercised	1,800,000	$ 100,000
Allocated Share-based Compensation Expense	$ 2,809,000	$ 3,004,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Estimated Forfeiture Rate	14.35%	12.47%
Stock Options [Member]
Allocated Share-based Compensation Expense	$ 100,000	$ 200,000
Unrecognized compensation cost related to non-vested awards granted	$ 900,000		$ 1,100,000
Weighted-average period to recognize compensation cost (in years)	2 years 10 months 17 days