v3.21.2

Unsecured Credit Agreements - Additional Information (Detail) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 15, 2021	Mar. 12, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Debt Instrument [Line Items]
Total unsecured debt			$ 1,597,868		$ 1,597,868		$ 1,547,667
Debt Instrument, Interest Rate, Stated Percentage			5.00%		5.00%
Cost of debt extinguishment			$ (242)	$ (392)	$ (368)	$ (414)
Other Nonoperating Income (Expense)
Debt Instrument [Line Items]
Cost of debt extinguishment			214	392	340	392
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs				5,918		5,918
2026 Unsecured Term Loan
Debt Instrument [Line Items]
Paydown amount		$ 50,000
Debt issuance costs incurred			4,069		5,020
2026 Unsecured Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.00%					1.60%
2026 Unsecured Term Loan | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		0.85%					1.45%
2026 Unsecured Term Loan | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		1.65%					2.40%
Modification of Existing Debt
Debt Instrument [Line Items]
Debt issuance costs incurred				$ 5,918		$ 5,918
Unamortized debt issuance costs			$ 3,379		$ 4,325
2031 Senior Unsecured Public Notes
Debt Instrument [Line Items]
Total unsecured debt	$ 375,000
Debt Instrument, Interest Rate, Stated Percentage	2.60%
Rate of Principal Amount	99.816%
Interest Rate Swap
Debt Instrument [Line Items]
Weighted average interest rate on all outstanding borrowings			2.71%		2.71%

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