Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 3) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	May 31, 2017	Dec. 31, 2016
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 6,956,443	$ 6,956,443		$ 7,076,758
Variable Rate Unsecured Term Loan $100 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate	LIBOR
Debt instrument, basis spread on variable rate (as a percent)	0.90%
Variable Rate Unsecured Term Loan $150 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate	LIBOR
Debt instrument, basis spread on variable rate (as a percent)	1.50%
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	$ 256,727	256,727
Mortgage notes payable and unsecured notes	1,249,716	1,249,716
Secured notes | Notes Payable Maturities 2017
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	2,223	2,223
Mortgage notes payable and unsecured notes	21,601	21,601
Stated interest rate of unsecured notes (as a percent)			6.256%
Secured notes | Notes Payable Maturities 2018
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	7,258	7,258
Mortgage notes payable and unsecured notes	76,667	76,667
Secured notes | Notes Payable Maturities 2019
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,696	4,696
Mortgage notes payable and unsecured notes	$ 114,723	$ 114,723
Stated interest rate of unsecured notes (as a percent)	5.86%	5.86%
Secured notes | Notes Payable Maturities 2020
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	$ 3,624	$ 3,624
Mortgage notes payable and unsecured notes	118,729	118,729
Secured notes | Notes Payable Maturities 2021
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,551	3,551
Mortgage notes payable and unsecured notes	27,844	27,844
Secured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,795	3,795
Secured notes | Notes Payable Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,040	4,040
Secured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,310	4,310
Secured notes | Notes Payable Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,585	4,585
Mortgage notes payable and unsecured notes	84,835	84,835
Secured notes | Notes Payable Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,894	4,894
Secured notes | Notes Payable Maturities Thereafter
Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	213,751	213,751
Mortgage notes payable and unsecured notes	805,317	805,317
Secured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate of unsecured notes (as a percent)			3.61%
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	5,450,000	5,450,000
Unsecured notes | Notes Payable 6.100 Percent Maturities 2020
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000	$ 250,000
Stated interest rate of unsecured notes (as a percent)	6.10%	6.10%
Unsecured notes | Notes Payable 3.625 Percent Maturities 2020
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 400,000	$ 400,000
Stated interest rate of unsecured notes (as a percent)	3.625%	3.625%
Unsecured notes | Notes Payable Maturities 2021
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000	$ 250,000
Stated interest rate of unsecured notes (as a percent)	3.95%	3.95%
Unsecured notes | Variable Rate Unsecured Term Loan $300 Million
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000	$ 300,000
Unsecured notes | Variable Rate Unsecured Term Loan $300 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate		LIBOR
Debt instrument, basis spread on variable rate (as a percent)		1.45%
Unsecured notes | Notes payable maturing in 2022
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 450,000	$ 450,000
Stated interest rate of unsecured notes (as a percent)	2.95%	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	$ 100,000
Unsecured notes | Variable Rate Unsecured Term Loan $100 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate		LIBOR
Debt instrument, basis spread on variable rate (as a percent)		0.90%
Unsecured notes | Notes payable maturing in 2023
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 350,000	$ 350,000
Stated interest rate of unsecured notes (as a percent)	4.20%	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	$ 250,000
Stated interest rate of unsecured notes (as a percent)	2.85%	2.85%
Unsecured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%	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	$ 150,000
Unsecured notes | Variable Rate Unsecured Term Loan $150 Million | LIBOR
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate		LIBOR
Debt instrument, basis spread on variable rate (as a percent)		1.50%
Unsecured notes | Notes Payable 3.450 Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 525,000	$ 525,000
Stated interest rate of unsecured notes (as a percent)	3.45%	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	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%	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	$ 475,000
Stated interest rate of unsecured notes (as a percent)	2.95%	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	$ 300,000
Stated interest rate of unsecured notes (as a percent)	2.90%	2.90%
Unsecured notes | Notes Payable Maturities 2046
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 350,000	$ 350,000
Stated interest rate of unsecured notes (as a percent)	3.90%	3.90%
Unsecured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 400,000	$ 400,000
Stated interest rate of unsecured notes (as a percent)	3.35%	3.35%
Unsecured notes | Notes Payable Maturities 2047
Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000	$ 300,000
Stated interest rate of unsecured notes (as a percent)	4.15%	4.15%