Related Party Transactions - Schedule of fees charged to unconsolidated joint ventures (Details) - Unconsolidated joint ventures and third party managed properties - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Management fees	$ 19,105	$ 17,937	$ 10,064
Development and leasing fees	15,558	13,907	9,615
Fees charged to unconsolidated joint ventures	$ 34,663	$ 31,844	$ 19,679