Business Segments and Geographic Information - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)	Dec. 31, 2018 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	$ 1,821	$ 2,341	$ 4,417	$ 4,336
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	2,100	$ 2,600	3,700
Investment in joint venture	12,500		12,500		13,400
Geo Amey
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates, net of income tax provision	600	$ 200	1,800	$ 600
Investment in affiliate	$ 6,500		$ 6,500		$ 4,800