Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2018	Apr. 30, 2018	Feb. 28, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Notes Payable, Unsecured Notes and Credit Facility
Total mortgage notes payable, unsecured notes and Term Loans	$ 7,645,437			$ 7,645,437		$ 7,645,437		$ 7,404,313
Credit Facility	0			0		0		0
Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility	7,645,437			7,645,437		7,645,437		7,404,313
Gain (Loss) on Extinguishment of Debt				(642)	$ (24,162)	(1,039)	$ (24,162)
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	5,650,000			5,650,000		5,650,000		5,350,000
Variable rate notes	300,000			300,000		300,000		300,000
Total mortgage notes payable, unsecured notes and Term Loans	6,200,000			6,200,000		6,200,000
Amount of debt discount	10,666			10,666		10,666		10,850
Amount of deferred financing costs, net	37,091			37,091		37,091		36,386
Term Loans
Notes Payable, Unsecured Notes and Credit Facility
Variable rate notes	250,000			250,000		250,000		250,000
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	535,869			535,869		535,869		593,987
Variable rate notes	909,568			909,568		909,568		910,326
Total mortgage notes payable, unsecured notes and Term Loans	1,286,796			1,286,796		1,286,796
Amount of debt discount	16,271			16,271		16,271		16,351
Amount of deferred financing costs, net	10,131			10,131		10,131		$ 11,256
Notes Payable Maturities 2018 | Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Total mortgage notes payable, unsecured notes and Term Loans	51,449			$ 51,449		$ 51,449
Repayments of secured mortgages		$ 13,380	$ 11,038
Notes Payable Maturities 2033 [Member] | Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Repayments of secured mortgages	15,295
Gain (Loss) on Extinguishment of Debt	635
Prepayment penalty	282
Write off of deferred debt issuance cost	$ 353
Notes Payable Maturities 2043 [Member] | Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Repayments of secured mortgages			15,174
Gain (Loss) on Extinguishment of Debt			426
Prepayment penalty			152
Write off of deferred debt issuance cost			$ 274