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Expiration date of the operating loss carryforwards.

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Change in deferred tax assets due to release of valuation allowance for deferred income taxes.

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Expiration date of the research and development and orphan drug tax credit carryforward.

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Amount of increase (decrease) in additional paid in capital (APIC) resulting from a tax benefit (deficiency) associated with an share-based compensation plan other than an employee stock ownership plan (ESOP).

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible alternative minimum tax credit carryforwards.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
Income Taxes - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Income (loss) before income tax expense benefit (expense)		$ 260,194,000	$ (42,498,000)	$ (41,250,000)
Excess tax benefits from stock-based compensation		16,965,000
Unrecorded excess stock-based compensation tax benefits		81,400,000
Federal tax provision at statutory rate		35.00%	35.00%	35.00%
Income tax benefit (expense)		16,258,000us-gaap_IncomeTaxExpenseBenefit	(115,000)us-gaap_IncomeTaxExpenseBenefit	(7,000)us-gaap_IncomeTaxExpenseBenefit
Research and development credit and orphan drug credit, expiration dates		2024 through 2034
Alternative minimum tax credits	4,000,000	4,000,000
Valuation allowance increased (decreased)		104,800,000	22,100,000	(8,000,000)
Release of valuation allowance for deferred income taxes	33,403,000	33,403,000
Gross unrecognized tax that would decrease effective tax rate, if recognized	6,700,000	6,700,000
Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards	160,600,000	160,600,000
Operating loss carryforwards, expiration dates		2032 and 2033
Research and development credit and orphan drug credit	29,000,000	29,000,000
State [Member]
Income Taxes [Line Items]
Operating loss carryforwards	240,400,000	240,400,000
Operating loss carryforwards, expiration dates		At various dates between the years 2019 and 2033
California credit carryforwards [Member]
Income Taxes [Line Items]
Research and development credit and orphan drug credit	$ 13,800,000	$ 13,800,000