Segment Reporting Segment Reporting (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Rental income from real estate assets sold or held for sale, not classified as discontinued operations	$ 28,430	$ 55,674	$ 80,704
Operating expenses from real estate assets sold or held for sale, not classified as discontinued operations	(10,921)	(21,541)	(30,996)
Net operating income from real estate assets sold or held for sale, not classified as discontinued operations	$ 17,509	$ 34,133	$ 49,708