Commitments and Contingencies - Schedule of Restructuring Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 81	$ 281	$ 194
Restructuring expenses	824	1,168	647
Payments for restructuring	(1,024)	(1,081)
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	930	600	500
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses		600	100
Reversal of restructuring expenses	(106)
Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	0	0	0
Restructuring expenses	0	300
Payments for restructuring	0	(300)
Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0
Corporate, Non-Segment [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0
UNITED STATES | Operating Segments [Member] | United States Electrical Construction And Facilities Services
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	0	255	30
Restructuring expenses		638
Reversal of restructuring expenses	(106)
Payments for restructuring	(149)	(413)
UNITED STATES | Operating Segments [Member] | United States Mechanical Construction And Facilities Services
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	0	26	164
Restructuring expenses	6	230
Payments for restructuring	(32)	(368)
UNITED STATES | Operating Segments [Member] | United States Building Services
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	81	0	$ 0
Restructuring expenses	924	0
Payments for restructuring	(843)	$ 0
UNITED STATES | Operating Segments [Member] | Employee Severance [Member] | United States Electrical Construction And Facilities Services
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0
UNITED STATES | Operating Segments [Member] | Employee Severance [Member] | United States Mechanical Construction And Facilities Services
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	6
UNITED STATES | Operating Segments [Member] | Employee Severance [Member] | United States Building Services
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	924
UNITED STATES | Operating Segments [Member] | Facility Closing [Member] | United States Electrical Construction And Facilities Services
Restructuring Cost and Reserve [Line Items]
Reversal of restructuring expenses	(106)
UNITED STATES | Operating Segments [Member] | Facility Closing [Member] | United States Mechanical Construction And Facilities Services
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0
UNITED STATES | Operating Segments [Member] | Facility Closing [Member] | United States Building Services
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 0