Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 4) - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2020	Dec. 31, 2020	Aug. 31, 2020	Mar. 31, 2020	Feb. 29, 2020	Dec. 31, 2019
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 7,629,814,000				$ 7,355,371,000
Percentage of principle amount at which the entity may redeem some or all of the notes		100.00%
Variable rate unsecured credit facility		$ 0				0
Variable rate unsecured credit facility
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Available borrowing capacity		1,750,000,000
Outstanding balance of letters of credit		2,900,000				11,488,000
Variable rate unsecured credit facility		$ 0				0
Variable rate unsecured credit facility | LIBOR
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Interest Rate, Effective Percentage		0.92%
Debt instrument, basis spread on variable rate (as a percent)		0.775%
Other Letter of Credit [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Outstanding balance of letters of credit		$ 32,079,000				$ 24,939,000
Notes Payable Maturities 2020
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate (as a percent)			4.18%		3.08%
Notes Payable Maturities 2027
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate (as a percent)					2.38%
Unsecured notes
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 6,750,000,000
Unsecured notes | Minimum
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)		0.20%
Unsecured notes | Maximum
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)		0.45%
Unsecured notes | Notes Payable 3.625 Maturities 2020 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate (as a percent)				3.625%
Unsecured notes | Notes Payable Maturities 2021 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 0
Stated interest rate (as a percent)				3.95%
Unsecured notes | Floating Rate Unsecured Notes 300 Million
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Repayments of secured debt	$ 300,000,000
Unsecured notes | Notes payable maturing in 2022
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 450,000,000
Stated interest rate (as a percent)		2.95%
Unsecured notes | Variable Rate Unsecured Term Loan $100 Million
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 100,000,000
Unsecured notes | Variable Rate Unsecured Term Loan $100 Million | LIBOR
Mortgage 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
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 350,000,000
Stated interest rate (as a percent)		4.20%
Unsecured notes | Notes Payable 2.850 Maturities 2023
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 250,000,000
Stated interest rate (as a percent)		2.85%
Unsecured notes | Notes Payable 2024
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 300,000,000
Stated interest rate (as a percent)		3.50%
Unsecured notes | Variable Rate Unsecured Term Loan $150 Million
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 150,000,000
Unsecured notes | Variable Rate Unsecured Term Loan $150 Million | LIBOR
Mortgage 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
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 525,000,000
Stated interest rate (as a percent)		3.45%
Unsecured notes | Notes Payable 3.500 Maturities 2025
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 300,000,000
Stated interest rate (as a percent)		3.50%
Unsecured notes | Notes Payable 2.950 Maturities 2026
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 475,000,000
Stated interest rate (as a percent)		2.95%
Unsecured notes | Notes Payable 2.900 Maturities 2026
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 300,000,000
Stated interest rate (as a percent)		2.90%
Unsecured notes | Notes Payable Maturities 2027
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 400,000,000
Stated interest rate (as a percent)		3.35%
Unsecured notes | Notes Payable Maturities 2028
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 450,000,000
Stated interest rate (as a percent)		3.20%
Unsecured notes | Notes Payable Maturities 2029 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 450,000,000
Stated interest rate (as a percent)		3.30%
Unsecured notes | Notes Payable Maturities 2030
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 700,000,000
Stated interest rate (as a percent)		2.30%
Unsecured notes | Notes Payable Maturities 2031
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 600,000,000
Stated interest rate (as a percent)		2.45%
Unsecured notes | Notes Payable Maturities 2046
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 350,000,000
Stated interest rate (as a percent)		3.90%
Unsecured notes | Notes Payable Maturities 2047
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 300,000,000
Stated interest rate (as a percent)		4.15%
Unsecured notes | Notes Payable Maturities 2048
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes		$ 300,000,000
Stated interest rate (as a percent)		4.35%
Secured notes
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		$ 304,282,000
Mortgage notes payable and unsecured notes		575,532,000
Secured notes | Notes Payable Maturities 2021 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		9,304,000
Mortgage notes payable and unsecured notes		27,844,000
Secured notes | Notes payable maturing in 2022
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		9,918,000
Secured notes | Notes Payable Maturities 2023
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		10,739,000
Secured notes | Notes Payable 2024
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		11,677,000
Secured notes | Notes Payable Maturities 2025
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		12,408,000
Mortgage notes payable and unsecured notes		0
Secured notes | Notes Payable Maturities 2026
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		13,445,000
Secured notes | Notes Payable Maturities 2027
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		15,880,000
Mortgage notes payable and unsecured notes		236,100,000
Secured notes | Notes Payable Maturities 2028
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		20,707,000
Mortgage notes payable and unsecured notes		0
Secured notes | Notes Payable Maturities 2029 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		11,742,000
Mortgage notes payable and unsecured notes		66,250,000
Secured notes | Notes Payable Maturities 2030
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		12,384,000
Secured notes | Notes Payable Maturities Thereafter
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments		176,078,000
Mortgage notes payable and unsecured notes		$ 245,338,000