v3.20.2

Unsecured Credit Agreements - Summary of Unsecured Credit Agreements (Detail) - USD ($) $ in Thousands		6 Months Ended
	Feb. 07, 2020	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Carrying amount of debt		$ 2,038,172	$ 1,989,451
Long-term Debt		$ 2,038,172
2020 Unsecured Term Loan
Debt Instrument [Line Items]
Maturity Date		Aug. 31, 2020
2022 Unsecured Term Loan
Debt Instrument [Line Items]
Maturity Date	Feb. 28, 2022
Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt		$ 1,928,300	1,877,300
Debt issuance costs, net		(6,908)	(7,919)
Long-term Debt		$ 1,921,392	1,869,381
Unsecured Debt | Senior Guaranteed Notes Series A
Debt Instrument [Line Items]
Debt instrument, interest rate		4.84%
Maturity Date		Apr. 30, 2027
Carrying amount of debt		$ 150,000	150,000
Unsecured Debt | Senior Guaranteed Notes Series B
Debt Instrument [Line Items]
Debt instrument, interest rate		5.09%
Maturity Date		Jul. 31, 2028
Carrying amount of debt		$ 225,000	225,000
Unsecured Debt | Senior Guaranteed Notes Series C
Debt Instrument [Line Items]
Debt instrument, interest rate		5.19%
Maturity Date		Jul. 31, 2030
Carrying amount of debt		$ 100,000	100,000
Unsecured Debt | Senior Notes
Debt Instrument [Line Items]
Carrying amount of debt		$ 475,000	475,000
Unsecured Debt | 2020 Unsecured Term Loan
Debt Instrument [Line Items]
Interest Rate		one-month LIBOR + 1.25%
Maturity Date		Feb. 28, 2021
Carrying amount of debt		$ 240,000	300,000
Unsecured Debt | 2020 Unsecured Term Loan | 1 Month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.25%
Unsecured Debt | Unsecured Revolving Credit and Term Loan Agreement
Debt Instrument [Line Items]
Carrying amount of debt		$ 703,300	652,300
Unsecured Debt | Unsecured Revolving Credit and Term Loan Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Interest Rate		one-month LIBOR + 1.20%
Maturity Date		Jan. 31, 2022
Carrying amount of debt		$ 248,300	197,300
Unsecured Debt | Unsecured Revolving Credit and Term Loan Agreement | Revolving Credit Facility | 1 Month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.20%
Unsecured Debt | Unsecured Revolving Credit and Term Loan Agreement | 2023 Unsecured Term Loan
Debt Instrument [Line Items]
Interest Rate		one-month LIBOR + 1.35%
Maturity Date		Jan. 31, 2023
Carrying amount of debt		$ 265,000	265,000
Unsecured Debt | Unsecured Revolving Credit and Term Loan Agreement | 2023 Unsecured Term Loan | 1 Month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.35%
Unsecured Debt | Unsecured Revolving Credit and Term Loan Agreement | 2024 Unsecured Term Loan
Debt Instrument [Line Items]
Interest Rate		one-month LIBOR + 1.25%
Maturity Date		Jun. 30, 2024
Carrying amount of debt		$ 190,000	190,000
Unsecured Debt | Unsecured Revolving Credit and Term Loan Agreement | 2024 Unsecured Term Loan | 1 Month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.25%
Unsecured Debt | 2022 Unsecured Term Loan
Debt Instrument [Line Items]
Interest Rate		one-month LIBOR + 1.25%
Maturity Date		Feb. 28, 2022
Carrying amount of debt		$ 60,000
Unsecured Debt | 2022 Unsecured Term Loan | 1 Month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.25%
Unsecured Debt | 2026 Unsecured Term Loan
Debt Instrument [Line Items]
Interest Rate		one-month LIBOR + 1.85%
Maturity Date		Feb. 28, 2026
Carrying amount of debt		$ 450,000	$ 450,000
Unsecured Debt | 2026 Unsecured Term Loan | 1 Month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.85%

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