Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities	$ 9,800
Provision for income taxes	0	$ 0	$ 0
Deferred tax assets attributable to excess stock option benefits	12,683	$ 10,630
Increase (decrease) in net valuation allowance of deferred tax asset	50,000
Unrecognized tax benefits, interest and penalties	0
Options to purchase common stock
Income Taxes [Line Items]
Deferred tax assets attributable to excess stock option benefits	6,700
Internal Revenue Service (IRS)
Income Taxes [Line Items]
Net operating losses	$ 497,200
Internal Revenue Service (IRS) | Minimum
Income Taxes [Line Items]
Net operating loss carryforwards, expiry date	2024
Internal Revenue Service (IRS) | Research Tax Credit Carryforward
Income Taxes [Line Items]
Research and development tax credit carryforwards	$ 4,500
Internal Revenue Service (IRS) | Research Tax Credit Carryforward | Minimum
Income Taxes [Line Items]
Research and development tax credits, expiry date	2028
State and Local Jurisdiction
Income Taxes [Line Items]
Net operating losses	$ 245,400
State and Local Jurisdiction | Minimum
Income Taxes [Line Items]
Net operating loss carryforwards, expiry date	2016
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Taxes [Line Items]
Research and development tax credit carryforwards	$ 2,700
Foreign Tax Authority
Income Taxes [Line Items]
Net operating losses	$ 10,700