Concentration of Credit Risk - Additional Information (Detail)		9 Months Ended
Sep. 30, 2020 tenant State segment	Sep. 30, 2020 tenant State segment
Concentration of Credit Risk
Number of states with more than ten percent of tenant annual base rent \| State	1	1
Minimum percent share of each state annualized base rent	10.00%	10.00%
Number of reportable segments \| segment	4	4
Number of tenants with more than ten percent of annual base rent \| tenant	1	1
Minimum Percent Share Of Annualized Base Rent Accounted By Tenants	10.00%	10.00%
Medical Office Building
Concentration of Credit Risk
Percentage of annual base rent	62.60%	62.60%
Senior Housing-RIDEA
Concentration of Credit Risk
Percentage of annual base rent	14.00%	14.00%
Skilled Nursing Facilities
Concentration of Credit Risk
Percentage of annual base rent	13.70%	13.70%
Senior Housing
Concentration of Credit Risk
Percentage of annual base rent	9.70%	9.70%
MISSOURI
Concentration of Credit Risk
Percentage of annual base rent	11.40%	11.40%

Minimum percent share of annualized base rent accounted by tenants.

No definition available.

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- Definition

Minimum percent share of each state annualized base rent that company owned.

+ References

No definition available.

+ Details

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- Definition

Number of tenants with More than ten percent of annual base rent.

+ References

No definition available.

+ Details

Name:	gahr_NumberOfTenantsWithMoreThanTenPercentOfAnnualBaseRent
Namespace Prefix:	gahr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of annual base rent.

+ References

No definition available.

+ Details

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Namespace Prefix:	gahr_
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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

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- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

+ Details

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- 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

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- Details

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- Details

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- Details

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- Details

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- Details

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