Share-Based Compensation (Narrative) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Stock Option Plans [Member]	Jun. 30, 2012 Stock Option Plans [Member]	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2013 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	5,550
Shares available for future grant		2,781			2,541
Maximum term of grants		10 years
Options vested and exercisable, period		5 years
Weighted average grant-date fair value of stock options granted		$ 6.81	$ 4.74
Restricted stock granted				6
Weighted average grant date fair value of restricted stock granted				$ 23.50
Number of initial offerings								5
Number of additional offerings						5	8
Stock options authorized to issue to employees					4,050