Business Segments and Geographic Information - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of reportable business segments | segment			4
Equity in earnings of affiliates, net of income tax provision	$ 1,426	$ 2,131	$ 2,913	$ 3,250
Investment in affiliate	0		$ 0		$ 0
SACS
Schedule of Equity Method Investments [Line Items]
Ownership percentage in entity			50.00%
Equity in earnings of affiliates, net of income tax provision	1,200	900	$ 2,300	1,800
Investment in joint venture	12,300		$ 12,300		11,800
Geo Amey
Schedule of Equity Method Investments [Line Items]
Ownership percentage in entity			50.00%
Equity in earnings of affiliates, net of income tax provision	300	$ 1,100	$ 600	$ 1,400
Investment in affiliate	2,000		2,000		$ 1,300
Ravenhall, Australia
Schedule of Equity Method Investments [Line Items]
Provision for loss on contracts	$ 1,900		$ 1,900