Name:	star_IncentiveFeeAbstract
Namespace Prefix:	star_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of incentive fee waiver for income-based incentive fee.

No definition available.

Name:	star_IncentiveFeeWaiverInvestmentIncome
Namespace Prefix:	star_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount payable for incentive rights held by the managing member or general partner, of limited liability company (LLC) or limited partnership (LP).

No definition available.

Name:	star_IncentiveFeesPayable
Namespace Prefix:	star_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The number of components consisted in incentive fee.

No definition available.

Name:	star_NumberOfIncentiveFeeComponents
Namespace Prefix:	star_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The required annual rate of return on an investment to offset its costs.

No definition available.

Name:	star_PercentOfAnnualHurdleRate
Namespace Prefix:	star_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The required quarterly rate of return on an investment to offset its costs.

No definition available.

Name:	star_PercentOfQuarterlyHurdleRate
Namespace Prefix:	star_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The required annual rate of return on an investment to offset its costs.

No definition available.

Name:	star_PercentageOfDollarAmountOfPreIncentiveFeeNetInvestmentIncomeReturns
Namespace Prefix:	star_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of pre incentive fee net investment income returns which exceeds the hurdle rate but is less than or equal per annualized.

No definition available.

Name:	star_PercentageOfPreIncentiveFeeNetInvestmentIncomeReturnsWhichExceedsTheHurdleRateAsButIsLessThanOrEqualPerAnnualized
Namespace Prefix:	star_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of pre incentive fee net investment income returns which exceeds the hurdle rate as catch-up.

No definition available.

Name:	star_PercentageOfPreIncentiveFeeNetInvestmentIncomeReturnsWhichExceedsTheHurdleRateAsCatchUp
Namespace Prefix:	star_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of pre incentive fee net investment income returns which exceeds the hurdle rate but is less than or equal per calendar quarter.

No definition available.

Name:	star_PercentageOfPreIncentiveFeeNetInvestmentIncomeReturnsWhichExceedsTheHurdleRateButIsLessThanOrEqualCalendarQuarter
Namespace Prefix:	star_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of realized capital gains on a cumulative basis from inception through the end of the fiscal year.

No definition available.

Name:	star_PercentagePayableOfRealizedCapitalGainsOnCumulativeBasis
Namespace Prefix:	star_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Amount paid for incentive rights held by the managing member or general partner, of limited liability company (LLC) or limited partnership (LP).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 230
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477867/946-230-45-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 17
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-17