Investment in Unconsolidated Joint Ventures (Other Data) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Aggregate outstanding indebtedness to third parties	$ 338,590	$ 526,458
Fees earned from unconsolidated joint ventures	$ 7,200	$ 7,400	$ 6,000