Mortgages and Notes Payable (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2021 USD ($) numberOfLoans	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($) extension	Sep. 30, 2021 USD ($) numberOfLoans	Sep. 30, 2020 USD ($)	Oct. 19, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Mortgages and notes payable	$ 2,942,902,000			$ 2,942,902,000			$ 2,470,021,000
Unamortized debt issuance costs	(15,808,000)			(15,808,000)			(13,981,000)
Loss on debt extinguishment				(134,000)	$ (3,671,000)
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity on credit facility			$ 750,000,000				600,000,000
Additional borrowing capacity on revolving credit facility			$ 550,000,000
Number of additional extensions | extension			2
Term of optional extension			6 months
Deferred financing fees			$ 4,800,000
Loss on debt extinguishment			$ (100,000)
Amount outstanding on revolving credit facility	135,000,000			135,000,000
Outstanding letters of credit on revolving credit facility	100,000			100,000
Unused borrowing capacity on revolving credit facility	614,900,000			614,900,000
PAC Portfolio Acquisition [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (3,410,000)			$ (3,410,000)
Number of loans assumed in acquisition | numberOfLoans	4			4
Unsecured Bridge Facility Due 2022 [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity on credit facility	$ 200,000,000			$ 200,000,000
Term of optional extension	6 months
Deferred financing fees	$ 1,000,000			1,000,000
Amount outstanding on revolving credit facility	$ 88,000,000			88,000,000
Term of debt instrument	6 months
3.20% (3.363% effective rate) Notes due 2021 [Member]
Debt Instrument [Line Items]
Loss on debt extinguishment		$ (100,000)
Early repayment of debt		$ 150,000,000
Stated interest rate (in hundredths)		3.20%
Secured indebtedness [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	$ 493,887,000			493,887,000			93,350,000
Aggregate undepreciated book value of secured real estate assets	721,000,000			721,000,000
Secured indebtedness [Member] | PAC Portfolio Acquisition [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	398,643,000			398,643,000
Secured indebtedness [Member] | 4.27% (3.61% effective rate) mortgage loan due 08/2028 [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	$ 116,374,000			$ 116,374,000
Effective interest rate (in hundredths)	3.61%			3.61%
Secured indebtedness [Member] | 3.61% (3.19% effective rate) mortgage loan due 08/2029 [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	$ 85,049,000			$ 85,049,000
Effective interest rate (in hundredths)	3.19%			3.19%
Secured indebtedness [Member] | 3.40% (3.50% effective rate) mortgage loan due 04/2033 [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	$ 69,409,000			$ 69,409,000
Effective interest rate (in hundredths)	3.50%			3.50%
Secured indebtedness [Member] | 4.60% (3.73% effective rate) mortgage loan due 01/2037 [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	$ 131,221,000			$ 131,221,000
Effective interest rate (in hundredths)	3.73%			3.73%
Unsecured indebtedness [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	$ 2,464,823,000			$ 2,464,823,000			$ 2,390,652,000
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility interest rate basis			LIBOR
Interest rate, basis spread (in hundredths)			0.90%
Annual facility fee (in hundredths)			0.20%
London Interbank Offered Rate (LIBOR) [Member] | Unsecured Bridge Facility Due 2022 [Member]
Debt Instrument [Line Items]
Facility interest rate basis	LIBOR
Interest rate, basis spread (in hundredths)	0.85%
Annual facility fee (in hundredths)	0.20%
Subsequent Event [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Amount outstanding on revolving credit facility						$ 155,000,000
Outstanding letters of credit on revolving credit facility						100,000
Unused borrowing capacity on revolving credit facility						594,900,000
Subsequent Event [Member] | Unsecured Bridge Facility Due 2022 [Member]
Debt Instrument [Line Items]
Amount outstanding on revolving credit facility						$ 88,000,000