Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term Debt	$ 3,923,084	$ 3,919,544
Fixed Rate Mortgage Loans [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Oct. 01, 2036
Debt, Weighted Average Contractual Interest Rate	4.30%
Debt, Weighted Average Effective Interest Rate	4.00%
Long-term Debt	$ 272,749	342,020
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Mar. 15, 2049
Debt, Weighted Average Contractual Interest Rate	3.80%
Debt, Weighted Average Effective Interest Rate	4.00%
Long-term Debt	$ 3,239,609	2,944,752
Total credit facilities	264,680	484,383
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 3,658,404	3,435,161
Line of Credit [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Mar. 23, 2022
Debt, Weighted Average Contractual Interest Rate	1.00%
Debt, Weighted Average Effective Interest Rate	1.40%
Line of Credit [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total credit facilities		220,000
Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Jan. 05, 2022
Debt, Weighted Average Contractual Interest Rate	2.00%
Debt, Weighted Average Effective Interest Rate	2.10%
Term Loan [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total credit facilities	$ 264,680	264,383
London Interbank Offered Rate (LIBOR) [Member] | Variable Rate Mortgage Loans [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Jun. 02, 2027
Debt, Weighted Average Contractual Interest Rate	2.80%
Debt, Weighted Average Effective Interest Rate	2.90%
Long-term Debt	$ 146,046	$ 148,389