Summary of Significant Accounting Policies (Schedule of Fixed and Variable Lease Payments) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Fixed payments	$ 105,207			$ 311,503
Variable payments	25,372			70,710
Total Rental and Tenant Reimbursement Revenue	$ 130,579	$ 504,400	$ 124,518	$ 382,213	$ 372,491	$ 553,300