Stockholders' equity (Tables)

6 Months Ended

Jun. 30, 2012

Stock options and restricted stock units [Abstract]

Option award activity

The following is a summary of option award activity under the Emergent Plans:

	2006 Plan					2004 Plan
	Number of Shares			Weighted-Average Exercise Price		Number of Shares		Weighted-Average Exercise Price		Aggregate Intrinsic Value
Outstanding at December 31, 2011		3,090,909		$	17.35		53,156	$	8.86	$	6,238,427
Granted		726,291			15.75		-		-
Exercised		(43,491	)		9.23		-		-
Forfeited		(125,678	)		19.52		-		-
Outstanding at June 30, 2012		3,648,031		$	17.06		53,156	$	8.86	$	4,227,300
Exercisable at June 30, 2012		2,176,650		$	16.09		53,156	$	8.86	$	4,200,518

Restricted stock units activity

The following is a summary of restricted stock unit award activity under the 2006 Plan:

	Number of Shares			Weighted-Average Grant Price		Aggregate Intrinsic Value
Outstanding at December 31, 2011		635,500		$	20.89	$	10,714,450
Granted		363,197			15.75
Vested		(228,369	)		20.26
Forfeited		(33,545	)		20.10
Outstanding at June 30, 2012		736,783		$	18.58	$	11,162,262