Business Segments and Geographic Information - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)	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	$ 1,342	$ 1,693	$ 4,255	$ 4,943
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	1,100	1,100	$ 3,400	2,900
Investment in joint venture	10,400		$ 10,400		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	200	$ 700	$ 800	$ 2,100
Investment in affiliate	2,300		2,300		$ 1,300
Ravenhall, Australia
Schedule of Equity Method Investments [Line Items]
Provision for loss on contracts	$ 1,900		$ 1,900