Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2013

Stockholders' Equity [Abstract]

Summary of stock option activity

The following table represents the stock option activity for the six months ended June 30, 2013:

	Number of Shares			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value (in thousands)
Outstanding options at December 31, 2012		9,529,597		$	3.05		3.63	$	12,595
Granted		209,300		$	4.08
Exercised		(2,487,275	)	$	2.44
Forfeited		(177,383	)	$	4.33
Outstanding options at June 30, 2013		7,074,239		$	3.26		3.74	$	10,540
Options vested and expected to vest		7,028,726		$	3.26		3.72	$	10,493
Exercisable at June 30, 2013		5,551,822		$	3.11		3.18	$	8,872