Discontinued Operations and Assets Held for Sale Impairment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) a	Dec. 31, 2015 USD ($) a	Dec. 31, 2014 USD ($) buildings a $ / sqft
Impairment Charges	$ 18,018	$ 22,932	$ 49,106
Acres of Land with Impairment Charge | a	244	139	442
Number of Real Estate Properties Determined to be Impaired | buildings			6
Fair Value Measurement With Unobservable Inputs Rental Rate Per Square Foot | $ / sqft			12.50
buildings [Member]
Impairment Charges	$ 3,719	$ 3,406	$ 15,406
Fair Value Inputs, Cap Rate			8.50%
Land [Member]
Impairment Charges	$ 14,299	$ 19,526	$ 33,700