Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Long Lived Assets Held-for-sale [Line Items]
Depreciation	$ 6,700	$ 6,200	$ 20,300	$ 16,800
Proceeds from sale of property and equipment			1,737	667
Loss on disposal of property plant and equipment			(1,260)	$ 2,007
Impairment of long-lived assets held-for-use			6,400
Heavy Civil Marine Construction
Long Lived Assets Held-for-sale [Line Items]
Proceeds from sale of property and equipment			300
Loss on disposal of property plant and equipment			200
Heavy Civil Marine Construction | Other Nonoperating Income (Expense)
Long Lived Assets Held-for-sale [Line Items]
Impairment of long-lived assets to be disposed of			$ 1,700