Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Long Lived Assets Held-for-sale [Line Items]
Depreciation	$ 6.8	$ 5.2	$ 13.6	$ 10.6
Impairment of long-lived assets held-for-use			6.4
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			$ 1.7