Concentration of Risk and Enterprise Wide Disclosures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended	9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Contract revenues	Sep. 30, 2014 Customer concentration risk Trade and contract retainage receivables	Dec. 31, 2013 Customer concentration risk Trade and contract retainage receivables	Sep. 30, 2014 Customer concentration risk Contract revenues	Sep. 30, 2013 Customer concentration risk Contract revenues	Sep. 30, 2014 Customer concentration risk Contract revenues	Sep. 30, 2013 Customer concentration risk Contract revenues	Sep. 30, 2013 Customer concentration risk U.S. Army Corps of Engineers Contract revenues	Sep. 30, 2013 Customer concentration risk U.S. Army Corps of Engineers Contract revenues	Sep. 30, 2014 Customer concentration risk Private Sector Customer Contract revenues	Sep. 30, 2014 Customer concentration risk Private Sector Customer Contract revenues	Sep. 30, 2014 Customer concentration risk Second Private Sector Customer Trade and contract retainage receivables	Dec. 31, 2013 Customer concentration risk Second Private Sector Customer Trade and contract retainage receivables	Sep. 30, 2014 Customer concentration risk Local port authority [Member] Trade and contract retainage receivables	Sep. 30, 2014 Customer concentration risk Federal Government Trade and contract retainage receivables	Dec. 31, 2013 Customer concentration risk Federal Government Trade and contract retainage receivables	Sep. 30, 2014 Customer concentration risk Federal Government Contract revenues	Sep. 30, 2013 Customer concentration risk Federal Government Contract revenues	Sep. 30, 2014 Customer concentration risk Federal Government Contract revenues	Sep. 30, 2013 Customer concentration risk Federal Government Contract revenues	Sep. 30, 2014 Customer concentration risk State Governments Trade and contract retainage receivables	Dec. 31, 2013 Customer concentration risk State Governments Trade and contract retainage receivables	Sep. 30, 2014 Customer concentration risk State Governments Contract revenues	Sep. 30, 2013 Customer concentration risk State Governments Contract revenues	Sep. 30, 2014 Customer concentration risk State Governments Contract revenues	Sep. 30, 2013 Customer concentration risk State Governments Contract revenues	Sep. 30, 2014 Customer concentration risk Local Governments Trade and contract retainage receivables	Dec. 31, 2013 Customer concentration risk Local Governments Trade and contract retainage receivables	Sep. 30, 2014 Customer concentration risk Local Governments Contract revenues	Sep. 30, 2013 Customer concentration risk Local Governments Contract revenues	Sep. 30, 2014 Customer concentration risk Local Governments Contract revenues	Sep. 30, 2013 Customer concentration risk Local Governments Contract revenues	Sep. 30, 2014 Customer concentration risk Private Companies Trade and contract retainage receivables	Dec. 31, 2013 Customer concentration risk Private Companies Trade and contract retainage receivables	Sep. 30, 2014 Customer concentration risk Private Companies Contract revenues	Sep. 30, 2013 Customer concentration risk Private Companies Contract revenues	Sep. 30, 2014 Customer concentration risk Private Companies Contract revenues	Sep. 30, 2013 Customer concentration risk Private Companies Contract revenues
Concentration Risk [Line Items]
Trade and retainage receivables						$ 47,617	$ 49,537												$ 1,014	$ 4,849					$ 2,532	$ 4,002					$ 14,171	$ 8,857					$ 29,900	$ 31,829
Concentration risk, percentage						100.00%	100.00%	100.00%	100.00%	100.00%	100.00%	9.30%	13.70%	11.50%	9.70%	25.80%	9.90%	10.20%	2.00%	10.00%	6.00%	16.00%	9.00%	20.00%	5.00%	8.00%	14.00%	10.00%	12.00%	9.00%	30.00%	18.00%	20.00%	14.00%	20.00%	16.00%	63.00%	64.00%	60.00%	60.00%	59.00%	55.00%
Contract revenues	$ 106,976	$ 88,992	$ 278,485	$ 248,131	$ 106,976				$ 88,992	$ 278,485	$ 248,131										$ 6,246	$ 14,193	$ 24,639	$ 50,685			$ 15,490	$ 9,339	$ 33,282	$ 21,355			$ 21,413	$ 12,359	$ 55,505	$ 38,545			$ 63,827	$ 53,101	$ 165,059	$ 137,546