Schedule of Restructuring Activities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 49	$ 474	$ 49	$ 474	$ 201	$ 81
Restructuring expenses	46	539	954	1,271
Payments for restructuring			(1,106)	(878)
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	46	539	954	1,271
UNITED STATES | Operating Segments [Member] | United States Mechanical Construction And Facilities Services [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	0	293	0	293	188	0
Restructuring expenses			181	401
Payments for restructuring			(369)	(108)
UNITED STATES | Operating Segments [Member] | United States Building Services [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 49	$ 181	49	181	$ 13	$ 81
Restructuring expenses			773	870
Payments for restructuring			$ (737)	$ (770)