Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Details) - Series I 2 [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Preferred Units [Line Items]
Amount	$ 7,537
Units (in units)	301,483
Liquidation preference	$ 25
Dividend rate	6.25%
Preferred Units, Total Annual Cash Distributions	$ 472	$ 472	$ 472