Name:	port_DeferredTaxAssetImpairmentOfEquityInvestment
Namespace Prefix:	port_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from gain on sale.

No definition available.

Name:	port_DeferredTaxAssetsDeferredGainOnSale
Namespace Prefix:	port_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from depreciation and amortization.

No definition available.

Name:	port_DeferredTaxAssetsDepreciationAndAmortization
Namespace Prefix:	port_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from digital asset impairment losses.

No definition available.

Name:	port_DeferredTaxAssetsDigitalAssetImpairment
Namespace Prefix:	port_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary difference from in-process research and development cost acquired in business combination or from joint venture formation or both.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-6

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

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-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

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

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards.

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

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from reserves and accruals.

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

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

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