Disposition Of Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of subsidiary									$ 0	$ 1,108	$ 0
Loss on sale of subsidiary									0	608	0
Gain on sale of building	$ 0	$ 0	$ 0	$ 0	$ 0	$ 11,749	$ 0	$ 0	$ 0	11,749	$ 0
United States Building Services | United States Building Services Subsidiary
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of subsidiary										1,100
Selling, General and Administrative Expenses | United States Building Services | United States Building Services Subsidiary
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on sale of subsidiary										$ 600
Gain on Sale of Building | United States Mechanical Construction And Facilities Services
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of building						$ 11,700