Planned Divestiture of Texas Heavy Civil Business Unit (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Planned Divestiture
Goodwill impairment charge		$ 401	$ 2,716	$ 401
Revenue and gross profit
% of Revenue			10.10%	11.40%	11.30%
Balance sheet information
Property, plant and equipment, net		283,545	$ 277,346	$ 283,545
Costs and estimated earnings in excess of billings		116,455	138,618	116,455
Billings in excess of costs and estimated earnings		139,875	112,606	139,875
Reserve for estimated losses on uncompleted contracts		$ 7,261	$ 12,801	$ 7,261
East
Revenue and gross profit
% of Revenue			(3.10%)	6.90%	5.30%
Texas Heavy Civil Business unit | JCG | East
Planned Divestiture
Charge against income	$ 37,300
Goodwill impairment charge	2,716
Texas Heavy Civil Business unit | JCG | East | Belton Texas area projects
Revenue and gross profit
Revenue	$ 10,000