Concentrations Risk - Additional Information (Detail)	3 Months Ended
Mar. 31, 2021 Property
Wholly Owned Properties [Member]
Concentration Risk [Line Items]
Number of properties	82
California [Member]
Concentration Risk [Line Items]
Number of properties	18
Lease Income [Member] \| Credit Concentration Risk [Member] \| California [Member]
Concentration Risk [Line Items]
Percentage of concentrations risk	23.90%
Rentable Square Feet [Member] \| Credit Concentration Risk [Member] \| California [Member]
Concentration Risk [Line Items]
Percentage of concentrations risk	17.90%
U.S. Government [Member] \| Lease Income [Member] \| Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Percentage of concentrations risk	98.60%
Non Governmental Tenants [Member] \| Lease Income [Member] \| Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Percentage of concentrations risk	1.40%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13531-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13537-108611

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration