Notes Payable and Unsecured Credit Facilities - Schedule of Debt Net of Unamortized Debt Premium (Discount) and Debt Issuance Costs (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Long-term Debt		$ 3,716,717	$ 3,718,944
Fixed Rate Mortgage Loans [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate		4.00%
Debt, Weighted Average Effective Interest Rate		3.50%
Long-term Debt		$ 356,541	359,414
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate		3.80%
Debt, Weighted Average Effective Interest Rate		4.00%
Long-term Debt		$ 3,245,087	3,243,991
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 3,716,717	3,718,944
Line of Credit [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate	[1]	1.10%
Debt, Weighted Average Effective Interest Rate	[1]	1.40%
London Interbank Offered Rate (LIBOR) [Member] | Variable Rate Mortgage Loans [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate	[2]	3.20%
Debt, Weighted Average Effective Interest Rate	[2]	3.30%
Long-term Debt	[2]	$ 115,089	$ 115,539

[1] Weighted average effective rate for the Line is calculated based on a fully drawn Line balance.

[2] Four of these variable rate loans have interest rate swaps in place to mitigate the interest rate fluctuation risk. Based on these swap agreements, the effective fixed rates of the four loans range from 2.5% to 4.1%.