Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended					6 Months Ended	12 Months Ended
	Dec. 29, 2017	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Dec. 31, 2017
Other Ownership Interests [Line Items]
Distributions declared per common share (in dollars per share)		$ 0.16				$ 0.16		$ 0.65
Cash Distributions		$ 22,126	$ 310,078	$ 22,224	$ 21,935	$ 21,614		$ 375,851
Distributions Reinvested		22,294	22,890	23,031	22,953	22,883		91,757
Total Declared		44,420	332,968	45,255	44,888	44,497		467,608
Distributions declared, noncontrolling interest		$ 60	$ 1,064	$ 1,786	21,053	$ 2,804		$ 26,707
Forecast
Other Ownership Interests [Line Items]
Distributions declared per common share (in dollars per share)							$ 0.65
Distributions declared per common share per month (in dollars per share)							0.0541667
Distributions declared per common share per month, return portion of stockholders' invested capital							$ 0.02
Aviva Coral Gables JV Loan
Other Ownership Interests [Line Items]
Distributions declared, noncontrolling interest					$ 21,000
Special Distribution Declared December 29, 2017
Other Ownership Interests [Line Items]
Distributions declared per common share (in dollars per share)	$ 1.05
Cash Distributions	$ 288,000