Share-Based Compensation (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Stock Option Plans [Member]	Mar. 31, 2013 Stock Option Plans [Member]	Mar. 31, 2014 Restricted Stock [Member]	Mar. 31, 2013 Restricted Stock [Member]	Mar. 31, 2014 Employee Stock Purchase Plan (ESPP) [Member]	Apr. 12, 2011 Employee Stock Purchase Plan (ESPP) [Member] offering	Feb. 12, 2004 Employee Stock Purchase Plan (ESPP) [Member] offering	Jan. 01, 2000 Employee Stock Purchase Plan (ESPP) [Member] offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	5,065,000
Shares available for future grant		2,262,000				2,476,000
Maximum term of grants		10 years
Options vested and exercisable, period		5 years
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 8.24	$ 8.24	$ 6.81
Restricted stock granted				14,000	6,000
Weighted average grant date fair value of restricted stock granted				$ 28.02	$ 23.50
Number of initial offerings									5
Requisite service period for plan participation eligibility						2 years
Number of additional offerings							5	8
Stock options authorized to issue to employees						4,050,000