Notes Payable and Revolving Lines of Credit - Schedule of Components of Notes Payable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Notes payable, net	$ 4,137,213	$ 3,738,497
Notes Payable
Debt Instrument [Line Items]
Total	4,167,149	3,763,474
Unamortized debt issuance costs	(29,936)	(24,977)
Notes payable, net	4,137,213	3,738,497
Notes Payable | Secured notes payable
Debt Instrument [Line Items]
Fixed rate notes payable	2,032,414	2,095,495
Variable rate notes payable	$ 834,735	717,979
Notes Payable | Secured notes payable | Minimum
Debt Instrument [Line Items]
Fixed Rate	2.50%
Variable Rate	3.90%
Notes Payable | Secured notes payable | Maximum
Debt Instrument [Line Items]
Fixed Rate	6.00%
Variable Rate	4.10%
Notes Payable | Secured notes payable | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.40%
Notes Payable | Secured notes payable | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.60%
Notes Payable | Unsecured notes payable
Debt Instrument [Line Items]
Fixed rate notes payable	$ 990,000	600,000
Variable rate notes payable	$ 310,000	$ 350,000
Variable Rate	3.80%
Notes Payable | Unsecured notes payable | Minimum
Debt Instrument [Line Items]
Fixed Rate	3.40%
Notes Payable | Unsecured notes payable | Maximum
Debt Instrument [Line Items]
Fixed Rate	4.40%
Notes Payable | Unsecured notes payable | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.30%