Schedule of Restructuring Activities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 736	$ 209	$ 736	$ 209	$ 1,630	$ 492
Restructuring expenses	119	229	567	693
Payments for restructuring			(1,461)	(976)
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	100	200	600	700
UNITED STATES | Operating Segments [Member] | United States Electrical Construction And Facilities Services [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	0	122	0	122	30	452
Restructuring expenses			0	0
Payments for restructuring			(30)	(330)
UNITED STATES | Operating Segments [Member] | United States Building Services [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	35	87	35	87	176	40
Restructuring expenses			567	693
Payments for restructuring			(708)	(646)
UNITED STATES | Operating Segments [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 701	$ 0	701	0	$ 1,424	$ 0
Restructuring expenses			0	0
Payments for restructuring			$ (723)	$ 0