Impairment and Related Charges (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Income Statement Elements [Abstract]
Impairment of Real Estate			$ 22,900
Impairment of Intangible Assets, Finite-lived			17,700
Goodwill, Impairment Loss			27,244
Gain (Loss) on Sale of Assets and Asset Impairment Charges	$ (11,000)	$ (28,148)	(67,805)	$ 0
Impairment and related charges	$ 17,100	$ 17,112	$ 67,805	$ 0