Share-based Compensation Arrangement By Share-based Payment Award, Performance Measurement, Percentage

No definition available.

Name:	mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceMeasurementPercentage
Namespace Prefix:	mgni_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

+ Details

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-3

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-7

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-6

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

+ References

+ Details

Name:	us-gaap_DebtInstrumentConvertibleNumberOfEquityInstruments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=mgni_ConvertibleSeniorNoteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_ConvertibleDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_ConvertibleDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=mgni_PerformanceSharesGrantedIn2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=mgni_PerformanceSharesGrantedIn2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=mgni_PerformanceSharesGrantedIn2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=mgni_PerformanceSharesGrantedIn2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=mgni_PerformanceSharesGrantedIn2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Net Income (Loss) Per Share - Narrative (Details)	3 Months Ended		9 Months Ended
Net Income (Loss) Per Share - Narrative (Details)	Sep. 30, 2025 equityInstrument	Sep. 30, 2024 equityInstrument	Sep. 30, 2025 equityInstrument	Sep. 30, 2024 equityInstrument	Feb. 01, 2025
Convertible Senior Notes \| Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion ratio			0.0156539
Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of shares issuable assuming conversion (in shares)	3,210,098	3,210,098	3,210,098	3,210,098
Performance Shares, Granted in 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage	0.00%	0.00%	0.00%	0.00%
Performance Shares, Granted in 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage	150.00%	115.00%	150.00%	115.00%
Performance Shares, Granted in 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage	150.00%	150.00%	150.00%	150.00%
Performance Shares, Granted in 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage	150.00%		150.00%
Performance Shares, Granted in 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage		99.00%		99.00%	125.00%