Property and Equipment Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Long Lived Assets Held-for-sale [Line Items]
Depreciation expense	$ 26.9	$ 23.7	$ 23.5
Impairment of Long-Lived Assets Held-for-use	6.4
Other Nonoperating Income (Expense)
Long Lived Assets Held-for-sale [Line Items]
Impairment of Long-Lived Assets Held-for-use	0.9
Other Nonoperating Income (Expense) | Heavy Civil Marine Construction Segment
Long Lived Assets Held-for-sale [Line Items]
Impairment of Long-Lived Assets to be Disposed of	$ 1.7