Real Estate - Schedule of Development in Process Activities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($) property
Property, Plant and Equipment [Line Items]
Number of properties under development | property	3	5
Real estate under development	$ 120,297	$ 173,702
Transfers In	0
Capitalized Costs	45,867
Transfers Out	$ 99,272
Core Portfolio
Property, Plant and Equipment [Line Items]
Number of properties under development | property	1	2
Real estate under development	$ 7,759	$ 21,897
Transfers In	0
Capitalized Costs	6,320
Transfers Out	$ 20,458
Fund Portfolio | Fund II
Property, Plant and Equipment [Line Items]
Number of properties under development | property	0	0
Real estate under development	$ 7,462	$ 4,908
Transfers In	0
Capitalized Costs	2,554
Transfers Out	$ 0
Fund Portfolio | Fund III
Property, Plant and Equipment [Line Items]
Number of properties under development | property	1	2
Real estate under development	$ 21,242	$ 63,939
Transfers In	0
Capitalized Costs	36,117
Transfers Out	$ 78,814
Fund Portfolio | Fund IV
Property, Plant and Equipment [Line Items]
Number of properties under development | property	1	1
Real estate under development	$ 83,834	$ 82,958
Transfers In	0
Capitalized Costs	876
Transfers Out	$ 0