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Operating loss carry forwards expiration year.

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The amount of annual limitations on the use of all operating loss carryforwards available to reduce future taxable income.

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Operating loss carryforwards available for offsetting against future taxable income.

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Operating loss carryforwards net expected to expire unutilized and unavailable to offset future federal taxable income.

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Operating loss carryforwards not subject to expiration.

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Tax credit carry forward expiration year.

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Tax credit carryforwards expected to expire unutilized.

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Tax cuts and jobs Act of 2017, incomplete accounting, change in tax rate, deferred tax assets, provisional income tax (expense) benefit.

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The percentage of the amount of valuation allowance to deferred tax asset.

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

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

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Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Income tax expense	$ 0	$ 0
Percentage of valuation allowance against deferred tax assets	100.00%
Decrease in deferred tax assets valuation allowance	$ 3,400,000	5,400,000
U.S. corporate income tax rate	21.00%		34.00%
Provisional income tax due to reduction in deferred tax assets			$ 143,500
New York State [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards net, expected to expire unutilized and unavailable to offset future federal taxable income	$ 169,400,000
New York City [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards net, expected to expire unutilized and unavailable to offset future federal taxable income	$ 153,700,000
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Open tax period	Dec. 31, 1998
Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Open tax period	Dec. 31, 2019
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 246,300,000	230,000,000
Operating loss carryforwards, annual limitation	27,500
Operating loss carryforwards net, expected to expire unutilized and unavailable to offset future federal taxable income	207,000,000
Operating loss carryforwards available for offset future taxable income	39,300,000
Operating loss carryforwards for unlimited period	37,600,000
Federal [Member] \| Expire Between 2019 and 2037 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards available for offset future taxable income	$ 1,700,000
Federal [Member] \| Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration dates	2020
Federal [Member] \| Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration dates	2037
Federal [Member] \| Research and Development Tax Credit Carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 5,300,000	5,000,000
Tax credit carryforwards, expiration dates	2039
Tax credit carryforwards expected to expire unutilized	$ 100,000
State and City [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 11,200,000	11,200,000
Operating loss carryforwards, expiration dates	2039
Foreign [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 26,100,000	25,200,000
Federal and State [Member] \| Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Open tax period	Dec. 31, 2016
Federal and State [Member] \| Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Open tax period	Dec. 31, 2019
Minimum [Member] \| State and City [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 27,300,000	27,300,000
Maximum [Member]
Operating Loss Carryforwards [Line Items]
U.S. corporate income tax rate			35.00%
Maximum [Member] \| State and City [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 180,600,000	$ 167,300,000