Schedule of Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term Debt	$ 4,414,857	$ 3,919,544
Fixed Rate Mortgage Loans [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate	4.40%
Debt, Weighted Average Effective Interest Rate	3.90%
Long-term Debt	$ 351,914	342,020
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate	3.90%
Debt, Weighted Average Effective Interest Rate	4.00%
Long-term Debt	$ 2,945,429	2,944,752
Total credit facilities	969,457	484,383
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 3,445,400	3,435,161
Line of Credit [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate	2.50%
Debt, Weighted Average Effective Interest Rate	2.70%
Line of Credit [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total credit facilities	$ 705,000	220,000
Term Loan [Member]
Debt Instrument [Line Items]
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	$ 264,457	264,383
London Interbank Offered Rate (LIBOR) [Member] | Variable Rate Mortgage Loans [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Contractual Interest Rate	3.10%
Debt, Weighted Average Effective Interest Rate	3.20%
Long-term Debt	$ 148,057	$ 148,389