Stock-Based Compensation - Summary of Unrecognized Stock-Based Compensation (Detail) $ in Millions	6 Months Ended
Jun. 30, 2025 USD ($)
Restricted Stock Units Outstanding [Member]
Schedule Of Share Based Compensation Arrangements By Share Based Paymen tAward [Line Items]
Unrecognized Expense	$ 193.0
Weighted- Average Amortization Period (Years)	2 years 9 months 18 days
Performance Based Restricted Stock Units [Member]
Schedule Of Share Based Compensation Arrangements By Share Based Paymen tAward [Line Items]
Unrecognized Expense	$ 116.2
Weighted- Average Amortization Period (Years)	1 year 9 months 18 days
Restricted Stock [Member]
Schedule Of Share Based Compensation Arrangements By Share Based Paymen tAward [Line Items]
Unrecognized Expense	$ 148.1
Weighted- Average Amortization Period (Years)	4 years 8 months 12 days
Stock Options [Member]
Schedule Of Share Based Compensation Arrangements By Share Based Paymen tAward [Line Items]
Unrecognized Expense	$ 55.9
Weighted- Average Amortization Period (Years)	3 years

Schedule of share based compensation arrangements by share based payment award line items.

No definition available.

Name:	ionq_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymenTawardLineItems
Namespace Prefix:	ionq_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=ionq_PerformanceBasedRestrictedStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: