v3.21.2

Unsecured Credit Agreements - Summary of Unsecured Credit Agreements (Parenthetical) (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
1 Month LIBOR | Revolving Credit Facilities
Debt Instrument [Line Items]
Interest rate	1.00%
Daily LIBOR | Revolving Credit Facilities
Debt Instrument [Line Items]
Interest rate	1.00%
Unsecured Debt | 1 Month LIBOR
Debt Instrument [Line Items]
Interest rate	0.08%	0.14%
Unsecured Debt | 1 Month LIBOR | 2022 Unsecured Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%	1.25%
Unsecured Debt | 1 Month LIBOR | 2024 Unsecured Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%	1.25%
Unsecured Debt | 1 Month LIBOR | 2023 Unsecured Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate	1.10%	1.35%
Unsecured Debt | 1 Month LIBOR | 2026 Unsecured Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%	1.85%
Unsecured Debt | 1 Month LIBOR | Revolving Credit Facilities
Debt Instrument [Line Items]
Basis spread on variable rate		1.20%
Unsecured Debt | Daily LIBOR
Debt Instrument [Line Items]
Interest rate	0.07%

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+ References

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- Definition

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6036836-161870

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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