Summary of Significant Accounting Principles - Insurance Coverage (Details)	6 Months Ended
	Jun. 30, 2016 USD ($) levels policy	Dec. 31, 2015 USD ($)
Insurance Coverage [Line Items]
Number of insurance policies (policy) | policy	2
Accrual for insurance liabilities	$ 4,718,000	$ 7,998,000
Heavy Civil Marine Construction
Insurance Coverage [Line Items]
Levels of insurance coverage maintained by the Company | levels	3
Amount in excess of primary insurance coverage	$ 150,000,000
Heavy Civil Marine Construction | Other liability policies
Insurance Coverage [Line Items]
Primary limit of insurance coverage	1,000,000
Heavy Civil Marine Construction | Maritime employer's liability
Insurance Coverage [Line Items]
Primary limit of insurance coverage	10,000,000
Heavy Civil Marine Construction | Watercraft pollution policy
Insurance Coverage [Line Items]
Primary limit of insurance coverage	$ 5,000,000
Commercial Concrete Construction
Insurance Coverage [Line Items]
Levels of insurance coverage maintained by the Company | levels	2
Amount in excess of primary insurance coverage	$ 25,000,000
Commercial Concrete Construction | Other liability policies
Insurance Coverage [Line Items]
Primary limit of insurance coverage	$ 1,000,000