Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Long Lived Assets Held-for-sale [Line Items]
Depreciation	$ 6,200	$ 6,800	$ 12,500	$ 13,600
Assets Disposed of in Q2 2017			5,000
Proceeds from sale of property and equipment			5,547	888
Loss on disposal of property plant and equipment			(177)	$ (606)
Impairment of long-lived assets held-for-use			1,400
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			$ (500)