Schedule of Restructuring Activities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 1,057	$ 1,464	$ 1,558	$ 1,630
Restructuring expenses	69	275
Payments for restructuring	(570)	(441)
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	100	300
UNITED STATES | Operating Segments [Member] | United States Electrical Construction And Facilities Services [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	356	0	445	30
Restructuring expenses	0	0
Payments for restructuring	(89)	(30)
UNITED STATES | Operating Segments [Member] | United States Building Services [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	0	70	412	176
Restructuring expenses	69	275
Payments for restructuring	(481)	(381)
UNITED STATES | Operating Segments [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	701	1,394	$ 701	$ 1,424
Restructuring expenses	0	0
Payments for restructuring	$ 0	$ (30)