Common Stock (Schedule Of Information About Unvested Options) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Common Stock [Abstract]
Unvested options, Shares, beginning balance	3,799,250
Granted, Shares	2,894,500
Vested, Shares	(1,757,500)
Cancelled, Shares	(357,250)
Unvested options, Shares, ending balance	4,579,000
Unvested options, Weighted Average Grant Date Fair Value Per Share, beginning balance	$ 5.80
Granted, Weighted Average Grant Date Fair Value Per Share	$ 11.62
Vested, Weighted Average Grant Date Fair Value Per Share	$ 5.26
Canceled, Weighted Average Grant Date Fair Value Per Share	$ 8.19
Unvested options, Weighted Average Grant Date Fair Value Per Share, ending balance	$ 9.50