Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Long Lived Assets Held-for-sale [Line Items]
Depreciation	$ 6.2	$ 6.3	$ 16.8	$ 17.5
Other Nonoperating Income (Expense)
Long Lived Assets Held-for-sale [Line Items]
Impairment of long-lived assets held-for-use			0.9
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