Stock Options And Employee Stock Purchase Plan (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested share-based compensation arrangements	$ 39,874
Total intrinsic value of nonvested options	10,105	19,839	32,420
Total value of stock options exercised	16,252	17,174	11,050
Total intrinsic value of options exercisable	20,815	21,890	22,491
Total intrinsic value of all outstanding options	$ 30,920	$ 41,729	$ 54,911
1998 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance	5,850,000
2000 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance	10,000,000
Increase in number of shares of common stock available for issuance	4,150,000
2009 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares of common stock available for issuance	6,000,000
Stock option term	10 years
Shares reserved for issuance	15,425,000
Weighted average recognition period of unrecognized compensation cost	2 years 1 month 6 days
Amended 2009 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance	23,817,744
Increase in number of shares of common stock available for issuance	4,250,000
2000 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance	450,000
2010 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance	1,000,000
Shares available for grant	849,000