Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Oct. 31, 2016	May 31, 2016	Dec. 31, 2015
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 7,076,758			$ 6,481,291
Percentage of principle amount at which the entity may redeem some or all of the notes	100.00%
Unsecured notes
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 4,500,000
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 maturing in 2017
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 0
Unsecured notes | Notes Payable 6.100 Percent Maturities 2020
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000
Stated interest rate of unsecured notes (as a percent)	6.10%
Unsecured notes | Notes Payable 3.625 Percent Maturities 2020
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 400,000
Stated interest rate of unsecured notes (as a percent)	3.625%
Unsecured notes | Notes payable maturing in 2021
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 250,000
Stated interest rate of unsecured notes (as a percent)	3.95%
Unsecured notes | Term loan
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Mortgage notes payable and unsecured notes	$ 300,000
Unsecured notes | Term loan | LIBOR
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Debt instrument, basis spread on variable rate (as a percent)	1.45%
Unsecured notes | Notes payable maturing in 2022
Mortgage 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 | Notes Payable 4.200 Maturities 2023
Mortgage 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
Mortgage 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 2024
Mortgage 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 3.450 Maturities 2025 [Member]
Mortgage 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 [Member]
Mortgage 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 [Member]
Mortgage 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%		2.95%
Unsecured notes | Notes Payable 2.900 Maturities 2026 [Member]
Mortgage 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%	2.90%
Unsecured notes | Notes Payable Maturities 2046 [Member]
Mortgage 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%	3.90%
Secured notes
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	$ 283,477
Mortgage notes payable and unsecured notes	2,293,281
Secured notes | Notes payable maturing in 2017
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	18,539
Mortgage notes payable and unsecured notes	709,491
Secured notes | Notes payable maturing in 2018
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	17,793
Mortgage notes payable and unsecured notes	76,916
Secured notes | Notes payable maturing in 2019
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,696
Mortgage notes payable and unsecured notes	655,386
Secured notes | Notes Payable Maturities 2020 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,624
Mortgage notes payable and unsecured notes	118,729
Secured notes | Notes payable maturing in 2021
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,551
Mortgage notes payable and unsecured notes	27,844
Secured notes | Notes payable maturing in 2022
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	3,795
Secured notes | Notes Payable Maturities 2023 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,040
Secured notes | Notes Payable 2024
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,310
Secured notes | Notes Payable Maturities 2025 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,585
Mortgage notes payable and unsecured notes	84,835
Secured notes | Notes Payable Maturities 2026 [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	4,859
Secured notes | Notes Payable Maturities Thereafter [Member]
Mortgage Notes Payable, Unsecured Notes and Credit Facility
Secured notes payments	213,685
Mortgage notes payable and unsecured notes	$ 620,080