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v3.19.3.a.u2

Real Estate (Tenant Reimbursements) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Real Estate [Abstract] |  |  |
Tenant reimbursements | $ 21.2 | $ 22.4 | $ 21.9

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- Definition Tenant Expense Reimbursements + References No definition available. + Details
Name: | star_TenantExpenseReimbursements
Namespace Prefix: | star_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_RealEstateAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration