Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 3) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Aug. 31, 2020	Mar. 31, 2020	Feb. 29, 2020	Dec. 31, 2019
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 7,631,099				$ 7,355,371
Notes Payable Maturities 2020 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate of unsecured notes (as a percent)		4.18%		3.08%
Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate of unsecured notes (as a percent)				2.38%
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	305,567
Mortgage notes payable and unsecured notes	575,532
Secured notes | Notes Payable Maturities 2020 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	1,285
Mortgage notes payable and unsecured notes	0
Secured notes | Notes Payable Maturities 2021 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	9,304
Mortgage notes payable and unsecured notes	27,844
Secured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	9,918
Secured notes | Notes Payable Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	10,739
Secured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	11,677
Secured notes | Notes Payable Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	12,408
Secured notes | Notes Payable Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	13,445
Secured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	15,080
Mortgage notes payable and unsecured notes	236,100
Secured notes | Notes Payable Maturities 2028
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	20,607
Secured notes | Notes Payable Maturities 2029 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	11,742
Mortgage notes payable and unsecured notes	66,250
Secured notes | Notes Payable Maturities Thereafter
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	189,362
Mortgage notes payable and unsecured notes	245,338
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	6,750,000
Unsecured notes | Notes Payable Maturities 2021 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate of unsecured notes (as a percent)			3.95%
Unsecured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 450,000
Stated interest rate of unsecured notes (as a percent)	2.95%
Unsecured notes | Variable Rate Unsecured Term Loan $100 Million
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 100,000
Unsecured notes | Variable Rate Unsecured Term Loan $100 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)	0.90%
Unsecured notes | Notes payable 4.200 Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 350,000
Stated interest rate of unsecured notes (as a percent)	4.20%
Unsecured notes | Notes Payable 2.850 Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000
Stated interest rate of unsecured notes (as a percent)	2.85%
Unsecured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%
Unsecured notes | Variable Rate Unsecured Term Loan $150 Million
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 150,000
Unsecured notes | Variable Rate Unsecured Term Loan $150 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)	0.85%
Unsecured notes | Notes Payable 3.450 Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 525,000
Stated interest rate of unsecured notes (as a percent)	3.45%
Unsecured notes | Notes Payable 3.500 Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%
Unsecured notes | Notes Payable 2.950 Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 475,000
Stated interest rate of unsecured notes (as a percent)	2.95%
Unsecured notes | Notes Payable 2.900 Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	2.90%
Unsecured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 400,000
Stated interest rate of unsecured notes (as a percent)	3.35%
Unsecured notes | Notes Payable Maturities 2028
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 450,000
Stated interest rate of unsecured notes (as a percent)	3.20%
Unsecured notes | Notes Payable Maturities 2029 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 450,000
Stated interest rate of unsecured notes (as a percent)	3.30%
Unsecured notes | Notes Payable Maturities 2030 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 700,000
Stated interest rate of unsecured notes (as a percent)	2.30%
Unsecured notes | Notes Payable Maturities 2031 [Member]
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 600,000
Stated interest rate of unsecured notes (as a percent)	2.45%
Unsecured notes | Notes Payable Maturities 2046
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 350,000
Stated interest rate of unsecured notes (as a percent)	3.90%
Unsecured notes | Notes Payable Maturities 2047
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	4.15%
Unsecured notes | Notes Payable Maturities 2048
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Stated interest rate of unsecured notes (as a percent)	4.35%