Notes Payable and Unsecured Credit Facilities Schedule of maturities of long-term debt (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
2020	$ 30,065
2021	85,699
2022	282,645
2023	69,498
2024	346,045
Beyond 5 Years	3,208,015
Unamortized debt premium/(discount) and issuance costs	(33,439)
Total	3,988,528	$ 3,919,544
Unsecured Debt [Member]
Debt Instrument [Line Items]
Total	3,238,514	$ 2,944,752
Scheduled Principal Payments [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
2020	3,065
2021	11,598
2022	11,797
2023	10,124
2024	5,301
Beyond 5 Years	21,712
Unamortized debt premium/(discount) and issuance costs	0
Total	63,597
Mortgage Loan Maturities [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
2020	27,000
2021	74,101
2022	5,848
2023	59,374
2024	90,744
Beyond 5 Years	161,303
Unamortized debt premium/(discount) and issuance costs	3,442
Total	421,812
Unsecured Maturities [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
2020	0
2021	0
2022	265,000
2023	0
2024	250,000
Beyond 5 Years	3,025,000
Unamortized debt premium/(discount) and issuance costs	(36,881)
Total	$ 3,503,119

Long term debt maturities repayments of principal thereafter.

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