Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Construction	$ 464,624	$ 427,018	$ 1,005,457	$ 921,143
Large Project Construction	249,345	217,084	642,116	590,282
Construction Materials	89,936	107,274	200,363	229,442
Total revenue	803,905	751,376	1,847,936	1,740,867
Gross profit	107,674	96,083	220,120	199,212
Assets	1,785,267	1,696,549	1,785,267	1,696,549	$ 1,626,878
Reconciliation from Segment Totals to Consolidated [Abstract]
Gross profit	107,674	96,083	220,120	199,212
Selling, general and administrative expenses	54,194	45,262	159,032	143,811
Gain on sales of property and equipment	398	804	2,364	2,090
Other income (expense), net	(912)	1,766	(3,024)	6,234
Income before provision for income taxes	54,790	49,859	66,476	51,257
Construction [Member]
Segment Reporting Information [Line Items]
Construction	464,624	427,018	1,005,457	921,143
Large Project Construction [Member]
Segment Reporting Information [Line Items]
Large Project Construction	249,345	217,084	642,116	590,282
Construction Materials [Member]
Segment Reporting Information [Line Items]
Construction Materials	89,936	107,274	200,363	229,442
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from reportable segments	876,804	809,873	1,974,681	1,844,345
Gross profit	107,674	96,083	220,120	199,212
Depreciation, Depletion and Amortization, Nonproduction	14,151	14,301	38,205	39,869
Assets	770,156	713,110	770,156	713,110
Reconciliation from Segment Totals to Consolidated [Abstract]
Gross profit	107,674	96,083	220,120	199,212
Operating Segments [Member] | Construction [Member]
Segment Reporting Information [Line Items]
Revenue from reportable segments	464,624	427,018	1,005,457	921,143
Gross profit	71,530	60,471	147,519	119,950
Depreciation, Depletion and Amortization, Nonproduction	6,162	5,194	16,032	14,752
Assets	156,458	140,493	156,458	140,493
Reconciliation from Segment Totals to Consolidated [Abstract]
Gross profit	71,530	60,471	147,519	119,950
Operating Segments [Member] | Large Project Construction [Member]
Segment Reporting Information [Line Items]
Revenue from reportable segments	249,345	217,084	642,116	590,282
Gross profit	23,519	21,654	50,678	53,669
Depreciation, Depletion and Amortization, Nonproduction	1,821	3,308	4,809	8,311
Assets	322,800	271,878	322,800	271,878
Reconciliation from Segment Totals to Consolidated [Abstract]
Gross profit	23,519	21,654	50,678	53,669
Operating Segments [Member] | Construction Materials [Member]
Segment Reporting Information [Line Items]
Revenue from reportable segments	162,835	165,771	327,108	332,920
Gross profit	12,625	13,958	21,923	25,593
Depreciation, Depletion and Amortization, Nonproduction	6,168	5,799	17,364	16,806
Assets	290,898	300,739	290,898	300,739
Reconciliation from Segment Totals to Consolidated [Abstract]
Gross profit	12,625	13,958	21,923	25,593
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Elimination of Intersegment Revenue	(72,899)	(58,497)	(126,745)	(103,478)
Intersegment Eliminations [Member] | Construction [Member]
Segment Reporting Information [Line Items]
Elimination of Intersegment Revenue	0	0	0	0
Intersegment Eliminations [Member] | Large Project Construction [Member]
Segment Reporting Information [Line Items]
Elimination of Intersegment Revenue	0	0	0	0
Intersegment Eliminations [Member] | Construction Materials [Member]
Segment Reporting Information [Line Items]
Elimination of Intersegment Revenue	$ (72,899)	$ (58,497)	$ (126,745)	$ (103,478)