Stock-Based Compensation (Details 3) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended						1 Months Ended	6 Months Ended
	Jun. 30, 2012 Stock options	Jun. 30, 2011 Stock options	Jun. 30, 2012 Stock options	Jun. 30, 2011 Stock options	Jun. 30, 2012 Stock options Minimum	Jun. 30, 2011 Stock options Minimum	Jun. 30, 2012 Stock options Minimum	Jun. 30, 2011 Stock options Minimum	Jun. 30, 2012 Stock options Maximum	Jun. 30, 2011 Stock options Maximum	Jun. 30, 2012 Stock options Maximum	Jun. 30, 2011 Stock options Maximum	Jun. 30, 2012 Stock options 2004 and 2012 Plans	Jun. 30, 2011 Stock options 2004 and 2012 Plans	Jun. 30, 2012 Employee stock purchase plan issuances	Jun. 30, 2011 Employee stock purchase plan issuances	Jun. 30, 2012 Employee stock purchase plan issuances	Jun. 30, 2011 Employee stock purchase plan issuances	Jun. 30, 2012 Employee stock purchase plan issuances Minimum	Jun. 30, 2011 Employee stock purchase plan issuances Minimum	Jun. 30, 2012 Employee stock purchase plan issuances Minimum	Jun. 30, 2011 Employee stock purchase plan issuances Minimum	Jun. 30, 2012 Employee stock purchase plan issuances Maximum	Jun. 30, 2011 Employee stock purchase plan issuances Maximum	Jun. 30, 2012 Employee stock purchase plan issuances Maximum	Jun. 30, 2011 Employee stock purchase plan issuances Maximum	Jun. 30, 2012 RSUs 2004 and 2012 Plans Time-Based	Jun. 30, 2011 RSUs 2004 and 2012 Plans Time-Based	Jun. 30, 2012 RSAs 2004 and 2012 Plans Time-Based	Jun. 30, 2011 RSAs 2004 and 2012 Plans Time-Based	Feb. 29, 2012 RSAs 2004 and 2012 Plans Performance-Contingent	Jun. 30, 2012 RSAs 2004 and 2012 Plans Performance-Contingent item	Jun. 30, 2011 RSAs 2004 and 2012 Plans Performance-Contingent
Compensation Awards
Number of Compensation Awards Granted (in shares)													198,000	307,500
Number of Compensation Awards Granted (in shares)																											528,381	465,000	402,500	1,148,000	44,500	44,500	1,290,000
Weighted-Average Exercise Price (in dollars per share)													$ 20.01	$ 24.56
Weighted-Average Fair Value (in dollars per share)																											$ 18.45	$ 25.03	$ 18.11	$ 24.70		$ 18.11	$ 24.73
Number of possible performance conditions, achievement of which not probable																																1
Number of possible performance conditions																																3
Weighted-average assumptions
Risk-free interest rate, minimum (as a percent)	0.74%	1.94%	0.74%	1.94%											0.15%	0.07%	0.15%	0.07%
Risk-free interest rate, maximum (as a percent)	1.10%	2.57%	1.17%	2.57%											0.29%	0.54%	0.29%	0.54%
Expected life					5 years	5 years	5 years	5 years	6 years	6 years	6 years	6 years							6 months	6 months	6 months	6 months	2 years	2 years	2 years	2 years
Volatility (as a percent)					55.00%	53.00%	55.00%	49.00%	60.00%	55.00%	60.00%	55.00%							55.00%	48.00%	55.00%	48.00%	64.00%	50.00%	64.00%	50.00%
Weighted-average estimated fair value of ESPP issuances (in dollars per share)	$ 11.11	$ 13.09	$ 10.37	$ 12.41											$ 9.00	$ 9.25	$ 9.00	$ 9.25
Stockholders' equity (net capital deficiency):
Shares exercised			349,538
Shares exercised, Weighted-Average Exercise Price of Outstanding Options (in dollars per share)			$ 7.99
Total cash proceed			$ 2,792,007