Summary of Significant Accounting Policies - Schedule of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	$ 115,467	$ 113,683
Fixed rate notes receivable	0	20,942
Fixed rate notes payable and notes payable to trusts	2,985,731	2,774,242
Exchangeable senior notes	620,149	719,056
Carrying Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	119,735	120,230
Fixed rate notes receivable	0	20,608
Fixed rate notes payable and notes payable to trusts	3,022,414	2,815,085
Exchangeable senior notes	$ 575,000	$ 624,259