Stock Options And Employee Stock Purchase Plan (Stock Options) (Details) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Stock Options [Member]	Dec. 31, 2013 Stock Options [Member]
Number of Shares, Outstanding Beginning of Period	1,175,657
Number of options granted	0
Number of Shares, Exercised	(424,706)
Number of Shares, Canceled	(15,000)
Number of Shares, Outstanding Ending of Period	735,951
Number of Shares, Exercisable	623,739
Number of Shares, Vested and expected to vest	721,497
Weighted-Average Exercise Price, Outstanding Beginning of Period	$ 21.21
Weighted-Average Exercise Price, Granted	$ 0.00
Weighted-Average Exercise Price, Exercised	$ 15.59
Weighted-Average Exercise Price, Canceled	$ 31.07
Weighted-Average Exercise Price, Outstanding Ending of Period	$ 24.25
Weighted-Average Exercise Price, Exercisable	$ 23.72
Weighted-Average Exercise Price, Vested and expected to vest	$ 24.19
Weighted-Average Remaining Contractual Term, Outstanding (in years)	4 years 1 month 17 days
Weighted-Average Remaining Contractual Term, Exercisable (in years)	3 years 8 months 5 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	4 years 0 months 29 days
Aggregate Intrinsic Value, Outstanding	$ 18,476,543
Aggregate Intrinsic Value, Exercisable	15,991,979
Aggregate Intrinsic Value, Vested and expected to vest	18,163,534
Aggregate intrinsic values of options exercised	14,500,000	11,600,000
Unrecognized compensation cost related to non-vested awards granted			$ 1,000,000	$ 2,000,000
Weighted-average period to recognize compensation cost (in years)			1 year 7 months 21 days