Income Taxes (Tables)

12 Months Ended

Dec. 31, 2013

Income Taxes [Abstract]

Schedule of Deferred Tax Assets and Liabilities

	As of December 31,
	2013			2012
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	238,608		$	216,579
Research and development tax credits	37,453			32,066
Capitalized research and development	83,375			71,839
Stock-based compensation	7,703			12,972
Deferred revenue	4,760			4,906
Other	4,712			10,429
Total deferred tax assets	376,611			348,791
Deferred tax liabilities:
Deferred tax liability related to acquisition of Symphony Icon	(18,745		)	(18,745		)
Other	—			(340		)
Total deferred tax liabilities	(18,745		)	(19,085		)
Less: valuation allowance	(376,611		)	(348,451		)
Net deferred tax liabilities	$	(18,745	)	$	(18,745	)