Notes and Bonds Payable (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Feb. 24, 2022	Feb. 18, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Notes and bonds payable	$ 1,907,438,000				$ 1,801,325,000
Impact of settlement of forward-starting interest rate swap	(5,159,000)	$ (2,850,000)
Mortgages
Debt Instrument [Line Items]
Effective interest rate			6.17%	4.70%
Line of credit | $700 million Unsecured Credit Facility
Debt Instrument [Line Items]
Notes and bonds payable	$ 334,000,000				210,000,000
Effective interest rate	1.35%
Credit facility	$ 700,000,000
Medium-term notes | $200 million Unsecured Term Loan due 2024, net of issuance costs
Debt Instrument [Line Items]
Notes and bonds payable	$ 199,516,000				199,460,000
Effective interest rate	2.03%
Term-loan facility	$ 200,000,000
Medium-term notes | $150 million Unsecured Term Loan due 2026, net of issuance costs
Debt Instrument [Line Items]
Notes and bonds payable	$ 149,412,000				149,376,000
Effective interest rate	2.52%
Term-loan facility	$ 150,000,000
Senior notes | Senior Notes due 2025, net of discount and issuance costs
Debt Instrument [Line Items]
Notes and bonds payable	$ 249,107,000				249,040,000
Effective interest rate	4.08%
Senior notes | Senior Notes due 2028, net of discount and issuance costs
Debt Instrument [Line Items]
Notes and bonds payable	$ 296,738,000				296,612,000
Effective interest rate	3.84%
Senior notes | Senior notes due 2030, net of discount and issuance costs
Debt Instrument [Line Items]
Notes and bonds payable	$ 296,901,000				296,813,000
Effective interest rate	2.71%
Senior notes | Senior Notes due 2031, net of discount and issuance costs
Debt Instrument [Line Items]
Notes and bonds payable	$ 295,487,000				295,374,000
Effective interest rate	2.24%
Mortgages | Mortgage notes payable, net of discounts and issuance costs and including premiums
Debt Instrument [Line Items]
Notes and bonds payable	$ 86,277,000				$ 104,650,000
Effective interest rate	3.97%
Settled interest rate swaps
Debt Instrument [Line Items]
Impact of settlement of forward-starting interest rate swap	$ (5,159,000)	$ (2,850,000)
Settled interest rate swaps | Medium-term notes | $200 million Unsecured Term Loan due 2024, net of issuance costs
Debt Instrument [Line Items]
Notional amount	$ 75,000,000
Weighted average interest rate (percent)	2.37%
Basis spread on variable rate	100.00%
Settled interest rate swaps | Medium-term notes | $150 million Unsecured Term Loan due 2026, net of issuance costs
Debt Instrument [Line Items]
Notional amount	$ 100,000,000
Weighted average interest rate (percent)	2.23%
Basis spread on variable rate	95.00%
Settled interest rate swaps | Senior notes | Senior Notes due 2025, net of discount and issuance costs
Debt Instrument [Line Items]
Impact of settlement of forward-starting interest rate swap	$ 1,700,000
Treasury lock | Senior notes | Senior Notes due 2025, net of discount and issuance costs
Debt Instrument [Line Items]
Impact of settlement of forward-starting interest rate swap	$ 4,300,000