Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Long Lived Assets Held-for-sale [Line Items]
Depreciation	$ 6,200	$ 6,700	$ 18,700	$ 20,300
Assets Disposed of in Q2 2017			5,400
Proceeds from sale of property and equipment			6,361	1,737
Loss on disposal of property plant and equipment			(590)	$ (1,260)
Impairment of long-lived assets held-for-use			1,000
Insurance claims pending	$ 1,000		1,000
Marine Construction
Long Lived Assets Held-for-sale [Line Items]
Proceeds from sale of property and equipment			4,500
Loss on disposal of property plant and equipment			$ 900