Accounting for the Impairment or Disposal of Long-Lived Assets (Asset Impairments in Reportable Segments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Asset impairment charges	$ 3,879	$ 18,244	$ 117
Carolinas Richmond [Member]
Segment Reporting Information [Line Items]
Asset impairment charges	0	13,755	0
Minnesota [Member]
Segment Reporting Information [Line Items]
Asset impairment charges	3,879	0	0
Southeastern PA [Member]
Segment Reporting Information [Line Items]
Asset impairment charges	0	2,328	106
Other Segments [Member]
Segment Reporting Information [Line Items]
Asset impairment charges	$ 0	$ 2,161	$ 11