Name:	star_AccruedInterestAndOperatingLeaseIncomeReceivableNet
Namespace Prefix:	star_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This element represents net amount of other deferred expenses and other assets capitalized at the end of the reporting period.

No definition available.

Name:	star_DeferredExpensesAndOtherAssetsNet
Namespace Prefix:	star_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Carrying amount as of the balance sheet date of investments in land and buildings held for sale, including real estate considered to be inventory of the entity.

No definition available.

Name:	star_RealEstateAvailableAndHeldForSale
Namespace Prefix:	star_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Real Estate Investment Property, Accumulated Depreciation and Amortization

No definition available.

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

Real Estate Investment Property, Held for Use, Net

No definition available.

Name:	star_RealEstateInvestmentPropertyHeldForUseNet
Namespace Prefix:	star_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property, by the lessor or lessee, respectively. Such receivable is reduced by allowances attributable to, for instance, credit risk associated with a lessee.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 35
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=77913719&loc=d3e40879-112712

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e39927-112707

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e39896-112707

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

Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 4
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6812-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.13)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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

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.

No definition available.

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

Name:	us-gaap_RealEstatePropertiesAxis=star_NetLeaseAssetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RealEstatePropertiesAxis=star_OperatingPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RealEstatePropertiesAxis=star_RealEstatePropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RealEstatePropertiesAxis=star_ResidentialOperatingPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: