v3.21.2

Related Party Arrangements - Narrative - Disposition Fee (Details) - Advisor			6 Months Ended
	Mar. 06, 2020	Mar. 05, 2020	Jun. 30, 2021	Aug. 31, 2020
Related Party Transaction [Line Items]
Disposition fee, maximum percent of brokerage commission paid threshold	50.00%
Advisor \| Disposition fees
Related Party Transaction [Line Items]
Disposition fee, percentage of sales price		1.00%
Property sale disposition fee, maximum percentage of total sale price				0.50%
Operating expenses limitation as a percentage of average invested assets			2.00%
Operating expenses limitation as a percentage of net income			25.00%

Represents the percentage of total brokerage commissions paid to advisor for services provided in connection with the sale of a property or real estate-related asset.

+ References

No definition available.

+ Details

Name:	sfar_DispositionFeeMaximumBrokerageCommissionPaidThresholdPercent
Namespace Prefix:	sfar_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum limitation for disposition fees, expressed as a percentage of the sales price, to be paid to advisor for disposition of property.

+ References

No definition available.

+ Details

Name:	sfar_DispositionFeeMaximumPercentageOfSalesPrice
Namespace Prefix:	sfar_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Disposition Fee, Percentage of Sales Price

+ References

No definition available.

+ Details

Name:	sfar_DispositionFeePercentageofSalesPrice
Namespace Prefix:	sfar_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents amount of certain operating expenses that may be recorded on a rolling four quarter basis expressed as a percentage of average invested assets (if greater than the related applicable percentage applied to net income).

+ References

No definition available.

+ Details

Name:	sfar_OtherOperatingExpenseReimbursementPercentageOfAverageInvestedAssetsThreshold
Namespace Prefix:	sfar_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents amount of certain operating expenses that may be recorded on a rolling four quarter basis expressed as a percentage of net income (if greater than the related applicable percentage applied to average invested assets).

+ References

No definition available.

+ Details

Name:	sfar_OtherOperatingExpenseReimbursementPercentageOfNetIncomeThreshold
Namespace Prefix:	sfar_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Details

Name:	srt_CounterpartyNameAxis=sfar_SteadfastApartmentAdvisorLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=sfar_SteadfastApartmentAdvisorLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=sfar_DispositionFeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Steadfast Apartment REIT, Inc. 10-Q