Unrecognized Tax Benefits That Would Impact Valuation Allowance

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are not subject to expiration dates.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are subject to expiration dates.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to 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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns.

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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 (Details) - USD ($)	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Income tax provision	$ 31,000	$ 136,000	$ 258,000	$ 208,000	$ 1,079,000	$ (3,000)	$ 128,000	$ 333,000	$ 466,000	$ 461,000	$ 602,000	$ 458,000	$ 633,000	$ 1,537,000	$ 636,000
Net loss before income taxes	(70,980,000)	$ (56,641,000)	$ (86,668,000)	$ (108,544,000)	(119,032,000)	$ (84,435,000)	$ (60,382,000)	$ (25,890,000)	$ (195,212,000)	$ (86,272,000)	$ (251,853,000)	$ (170,707,000)	$ (322,833,000)	$ (289,739,000)	$ (294,392,000)
Effective income tax rate													(0.20%)	(0.50%)	(0.20%)
Valuation allowance	633,591,000				571,277,000								$ 633,591,000	$ 571,277,000
Increase (decrease) in valuation allowance													62,300,000	24,000,000
Uncertain tax positions increase													4,200,000
Unrecognized tax benefits that would result in adjustments to the valuation allowance	31,500,000												31,500,000
Interest and penalties accrued	0				$ 0								0	$ 0
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1,800,000,000												1,800,000,000
Operating loss carryforwards, subject to expiration	1,700,000,000												1,700,000,000
Operating loss carryforwards, not subject to expiration	100,000,000												100,000,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1,600,000,000												1,600,000,000
Research Tax Credit Carryforward \| Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	20,500,000												20,500,000
Research Tax Credit Carryforward \| State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	14,000,000												14,000,000
Investment Tax Credit Carryforward \| Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 6,600,000												$ 6,600,000