Segment Reporting Segment Reporting (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting [Abstract]
Rental income from real estate assets sold or held for sale, not classified as discontinued operations	$ 24,389	$ 30,867	$ 21,463
Operating expenses real estate assets sold or held for sale, not classified as discontinued operations	(9,190)	(11,419)	(7,687)
Net operating income from real estate assets sold or held for sale, not classified as discontinued operations	$ 15,199	$ 19,448	$ 13,776