Segment Information (Costs Incurred on Long-lived Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	$ 632,038	$ 503,000	$ 571,583
Operating Segments [Member] | North America [Member] | Carolinas Richmond [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	31,958	51,647	31,175
Operating Segments [Member] | North America [Member] | Chicago Minneapolis [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	14,246	29,317	54,742
Operating Segments [Member] | North America [Member] | Florida [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	23,832	38,312	43,594
Operating Segments [Member] | North America [Member] | Houston [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	17,522	25,831	98,559
Operating Segments [Member] | North America [Member] | Lehigh Central PA [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	89,304	176,386	165,319
Operating Segments [Member] | North America [Member] | Philadelphia [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	30,685	57,691	34,122
Operating Segments [Member] | North America [Member] | Southeastern PA [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	9,737	4,824	5,700
Operating Segments [Member] | North America [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	404,253	107,500	125,412
Operating Segments [Member] | United Kingdom [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Cost incurred on long-lived assets	$ 10,501	$ 11,492	$ 12,960