Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2012

Stockholders' Equity [Abstract]

Summary of stock option activity

	Number of Shares			Weighted Average Exercise Price ($)		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value ($)
Outstanding at December 31, 2011		7,785,672			1.21
Granted		1,314,731			3.17
Exercised		(1,034,636	)		1.21
Cancelled		(141,206	)		4.06
Outstanding at September 30, 2012		7,924,561			1.48		6.8		22,810,852
Exercisable at September 30, 2012		6,122,279			1.14		6.2		19,727,349

Assumptions used in fair value measurement of options granted

	September 30,
	2012			2011
Risk-free interest rate		0.7	%		1.7	%
Annualized volatility		61.0	%		58.5	%
Weighted average expected life, in years		5.0			5.0
Expected dividend yield		0.0	%		0.0	%

Summary of performance stock unit awards and stock option granted under long term incentive program

	Performance Stock Units				Stock Options
Grant Date	Number of Shares		Fair Value on Grant Date		Number of Options		Exercise Price
May 17, 2011		182,000	$	1.66		317,000	$	1.66
May 17, 2012		—		—		470,000	$	2.94
July 6, 2012		137,715	$	4.26		—		—