Period after which financial instrument has reached maturity.

No definition available.

Name:	sldp_FinancialInstrumentMaturityPeriod
Namespace Prefix:	sldp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value portion of asset recognized for present right to economic benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

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

- References

No definition available.

+ Details

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

- 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

+ Details

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

- Definition

Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-3

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value of financial and nonfinancial obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

Amount of investment in marketable security, classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

Amount of cash outflow for purchase of marketable security.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481830/320-10-45-11

+ Details

Name:	us-gaap_PaymentsToAcquireMarketableSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Fair Value Measurements - Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Fair Value Measurements
Marketable securities	$ 218,151	$ 218,151		$ 229,177
Investments	177,865	177,865		$ 86,997
Liabilities
Available-for-sale securities purchased		$ 245,450	$ 101,690
Commercial Paper \| Marketable securities \| Maximum
Fair Value Measurements
Financial Instrument Maturity Period		1 year		1 year
Corporate Bonds \| Marketable securities \| Maximum
Fair Value Measurements
Financial Instrument Maturity Period		1 year		1 year
Corporate Bonds \| Investments \| Maximum
Fair Value Measurements
Financial Instrument Maturity Period		5 years		5 years
Government Bonds \| Marketable securities \| Maximum
Fair Value Measurements
Financial Instrument Maturity Period		1 year		1 year
Government Bonds \| Investments \| Maximum
Fair Value Measurements
Financial Instrument Maturity Period		5 years		5 years
U.S. treasuries \| Marketable securities \| Maximum
Fair Value Measurements
Financial Instrument Maturity Period		1 year		1 year
Recurring \| Marketable securities
Fair Value Measurements
Marketable securities	218,151	$ 218,151		$ 229,177
Recurring \| Investments
Fair Value Measurements
Investments	177,865	177,865		86,997
Recurring \| Public Warrants \| Warrant liabilities
Liabilities
Liabilities	1,476	1,476		9,911
Recurring \| Private Placement Warrants \| Warrant liabilities
Liabilities
Liabilities	514	514		3,970
Recurring \| Level 1 \| Public Warrants \| Warrant liabilities
Liabilities
Liabilities	1,476	1,476		9,911
Recurring \| Level 2 \| Private Placement Warrants \| Warrant liabilities
Liabilities
Liabilities	514	514		3,970
Recurring \| Level 3
Liabilities
Transfers in or out of Level 3	0	0		0
Recurring \| Commercial Paper \| Marketable securities
Fair Value Measurements
Marketable securities	59,483	59,483		62,166
Assets
Assets	59,483	59,483		62,167
Recurring \| Commercial Paper \| Level 1 \| Marketable securities
Assets
Assets	59,483	59,483		62,167
Recurring \| Corporate Bonds \| Marketable securities
Fair Value Measurements
Marketable securities	126,309	126,309		122,941
Assets
Assets	126,309	126,309		122,941
Recurring \| Corporate Bonds \| Investments
Fair Value Measurements
Investments	152,413	152,413		63,187
Assets
Assets	152,413	152,413		63,187
Recurring \| Corporate Bonds \| Level 1 \| Marketable securities
Assets
Assets	126,309	126,309		122,941
Recurring \| Corporate Bonds \| Level 1 \| Investments
Assets
Assets	152,413	152,413		63,187
Recurring \| Government Bonds \| Marketable securities
Fair Value Measurements
Marketable securities	21,320	21,320		39,053
Assets
Assets	21,320	21,320		39,053
Recurring \| Government Bonds \| Investments
Fair Value Measurements
Investments	24,478	24,478		22,479
Assets
Assets	24,478	24,478		22,479
Recurring \| Government Bonds \| Level 1 \| Marketable securities
Assets
Assets	21,320	21,320		39,053
Recurring \| Government Bonds \| Level 1 \| Investments
Assets
Assets	24,478	24,478		22,479
Recurring \| U.S. treasuries \| Marketable securities
Fair Value Measurements
Marketable securities	11,039	11,039		5,017
Assets
Assets	11,039	11,039		5,017
Recurring \| U.S. treasuries \| Level 1 \| Marketable securities
Assets
Assets	11,039	11,039		5,017
Recurring \| Equity Method Investment \| Investments
Fair Value Measurements
Investments	974	974		1,331
Recurring \| Bifurcated embedded derivative \| Loan receivable from equity method investee
Assets
Assets	584	584		584
Recurring \| Bifurcated embedded derivative \| Level 3 \| Loan receivable from equity method investee
Assets
Assets	$ 584	$ 584		$ 584