Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term Debt	$ 3,919,544	$ 3,715,212
Fixed Rate Mortgage Loans [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Oct. 01, 2036
Debt, Weighted Average Contractual Interest Rate	4.40%
Debt, Weighted Average Effective Interest Rate	4.00%
Long-term Debt	$ 342,020	403,306
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Mar. 15, 2049
Debt, Weighted Average Contractual Interest Rate	3.90%
Debt, Weighted Average Effective Interest Rate	4.10%
Long-term Debt	$ 2,944,752	2,475,322
Total credit facilities	484,383	708,734
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 3,435,161	3,006,478
Line of Credit [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Mar. 23, 2022
Debt, Weighted Average Contractual Interest Rate	2.70%
Debt, Weighted Average Effective Interest Rate	2.90%
Line of Credit [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total credit facilities	$ 220,000	145,000
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	$ 264,383	563,734
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	3.20%
Debt, Weighted Average Effective Interest Rate	3.30%
Long-term Debt	$ 148,389	$ 127,850