Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details) - USD ($)	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Notes Payable, Unsecured Notes and Credit Facility
Total mortgage notes payable, unsecured notes and Term Loans	$ 7,422,232,000		$ 7,102,355,000
Credit Facility	0		0
Total mortgage notes payable, unsecured notes, Term Loans and Credit Facility	7,422,232,000		7,102,355,000
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	5,850,000,000		5,400,000,000
Variable rate notes	300,000,000		300,000,000
Total mortgage notes payable, unsecured notes and Term Loans	6,400,000,000
Amount of debt discount	8,977,000		9,879,000
Amount of deferred financing costs, net	34,133,000		34,128,000
Term Loans
Notes Payable, Unsecured Notes and Credit Facility
Variable rate notes	250,000,000		250,000,000
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	546,082,000		533,215,000
Variable rate notes	476,150,000		619,140,000
Total mortgage notes payable, unsecured notes and Term Loans	709,798,000
Amount of debt discount	14,501,000		14,590,000
Amount of deferred financing costs, net	3,342,000		3,495,000
Variable Rate Unsecured Term Loan $250 Million [Member] | Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Debt Instrument, Face Amount		$ 250,000,000
Line of Credit [Member]
Notes Payable, Unsecured Notes and Credit Facility
Credit Facility	$ 0		$ 0