Income Taxes (Income Tax Rate Reconciliation) (Detail)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective income tax rate continuing operations tax rate reconciliation [Abstract]
Federal income tax computed at the statutory rate	21.00%	21.00%	21.00%
Increase (reduction) in taxes resulting from: [Abstract]
Change in valuation allowance	(20.60%)	(20.30%)	(20.70%)
State income tax, net of federal benefit	0.00%	0.00%	(0.40%)
Other	(0.40%)	(0.70%)	(0.50%)
Effective tax rate	0.00%	0.00%	(0.60%)

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319

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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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-Topic 740
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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