Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023
Income Tax [Line Items]
Deferred tax assets, valuation allowance	$ 22.4		$ 22.4		$ 22.5
Decrease in unrecognized tax positions	2.4		2.4
Valuation allowance attributable to the unrealized holding loss on available for sale short-term investments	(1.2)		(1.2)		$ (1.3)
Favorable discrete adjustment	$ 4.5		$ 4.5
Effective tax rate impact associated with stock-based compensation and previously recorded tax reserves	0.20%	0.20%	0.60%	0.20%
Interest and penalties	$ 3.1		$ 3.1
Decrease in effective tax rate due to federal and state tax credits	(0.60%)	(0.30%)	(0.20%)	(0.10%)
Increase in valuation allowance		$ 1.4		$ 1.4
Effective tax rate benefit associated with worthless stock	9.30%	4.60%	2.60%	1.30%

Deferred tax assets available for sale short term investments valuation allowance.

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- Definition

Effective income tax rate reconciliation nondeductible expense share based compensation cost plus release of tax reserves.

+ References

No definition available.

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- Definition

Represents effective tax rate impact associated with stock-based compensation and other previously recorded reserves.

+ References

No definition available.

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- Definition

Income tax.

+ References

No definition available.

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- Definition

Tax benefit associated with write-off of IAMD subsidiary worthless stock.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-2

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- Definition

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 income tax settlements. Including, but not limited to, domestic tax settlement, foreign tax settlement, state and local tax settlement, and other tax settlements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.Fact.4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

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- Definition

The amount of the unrecognized tax benefit of a position taken for which it is reasonably possible that the total amount thereof will significantly increase or decrease within twelve months of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-15

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-15

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-2

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