Stock-Based Compensation (Options) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Employee Stock Purchase Plan
Employee Stock Purchase Plan Percent of Stock Price At Closing Date	85.00%
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period		10 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Estimated Value Granted During Period	$ 7,700,000	$ 10,500,000
Number of Shares
Options outstanding, beginning balance	2,663,000
Options granted	242,687	402,511
Options exercised	(70,000)
Options canceled	(16,000)
Options outstanding, ending balance	2,820,000
Options vested and expected to vest, outstanding	2,771,000
Options exercisable, end of period	1,914,000
Weighted Average Exercise Price
Options outstanding, Weighted Average Exercise Price, beginning balance	$ 21.12
Options granted, Weighted Average Exercise Price	$ 31.59
Options exercised, Weighted Average Exercise Price	$ 17.50
Options canceled, Weighted Average Exercise Price	$ 20.66
Options outstanding, Weighted Average Exercise Price, ending balance	$ 22.11
Options vested and expected to vest, Weighted Average Exercise Price	$ 22.02
Options exercisable, Weighted Average Exercise Price, end of period	$ 21.37
Weighted Average Remaining Contractual Term
Options outstanding, Weighted Average Remaining Contractual Term (in years)	5 years 6 months 1 day
Options vested and expected to vest, Weighted Average Remaining Contractual Term (in years)	5 years 5 months 8 days
Option exercisable, Weighted Average Remaining Contractual Term (in years)	4 years 1 month 25 days
Aggregate Intrinsic Value
Options outstanding, Aggregate Intrinsic Value	22,775,000
Options vested and expected to vest, Aggregate Intrinsic Value	22,600,000
Options exercisable, Aggregate Intrinsic Value	16,590,000
Unrecognized Compensation Cost
Total unrecognized compensation cost related to unvested awards	6,200,000
Nonvested awards, weighted average remaining period (in years)	2 years 2 months 24 days
Intrinsic value of stock options exercised	$ 1,000,000	$ 1,500,000