Name:	star_CapitalDistributionsFromEquityInvestments
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Early repayment amount and termination fees during the period.

No definition available.

Name:	star_EarlyRepaymentAndTerminationFees
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Reflects the carrying amount of loans deemed to be questionable as to collection on which interest is continuing to be earned or accrued.

No definition available.

Name:	star_LoansAndLeasesReceivablesImpairedNonperformingAccrualOfInterest
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Period between non-accrual status interest or dividend payments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	star_NonAccrualStatusInterestOrDividendPayments
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Number of investment on non-accrual status.

No definition available.

Name:	star_NumberOfInvestmentOnNonAccrualStatus
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The amount of payment-in-kind interest income.

No definition available.

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

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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-Subparagraph (SX 210.5-03(8))
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-Topic 470
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Data Type:	xbrli:monetaryItemType
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Amount, after accumulated amortization, of debt discount.

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Data Type:	xbrli:monetaryItemType
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The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

No definition available.

Name:	us-gaap_InterestAndOtherIncome
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Data Type:	xbrli:monetaryItemType
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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
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-Name Accounting Standards Codification
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Name:	us-gaap_InterestReceivable
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of dividend income on nonoperating securities.

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Data Type:	xbrli:monetaryItemType
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Amount of revenue and income classified as other.

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-Topic 946
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-Name Accounting Standards Codification
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-Paragraph 6
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-Topic 946
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-Topic 944
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(4))
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-Topic 946
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-Paragraph 1
-Subparagraph (SX 210.6-07(1)(c))
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Name:	us-gaap_OtherIncome
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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Amount of realized gain (loss) on investment.

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-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(a))
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-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Name:	us-gaap_RealizedInvestmentGainsLosses
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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- References

No definition available.