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Components of Net Deferred Tax Asset (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Deferred tax assets:    
Net operating loss carryforwards $ 609,471 $ 557,427
Research and development credits 65,315 59,848
Capitalized research 31,490 32,440
Accrued expenses 2,922 2,827
Non-qualified stock option expense 30,928 27,964
Depreciation 10,025 8,906
Total net deferred tax assets 750,151 689,412
Valuation allowance (750,151) (689,412)
Net deferred tax assets