Business Segments (Reportable Segments) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Revenue	$ 952,154	$ 1,207,595
Income (loss) from construction operations	(9,907)	49,704
Capital expenditures	12,028	9,835
Depreciation and amortization	20,238	26,874
Operating Segments
Segment Reporting Information [Line Items]
Revenue	1,047,584	1,365,262
Income (loss) from construction operations	4,603	62,645
Capital expenditures	11,815	9,782
Depreciation and amortization	17,903	24,104
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(95,430)	(157,667)
Corporate
Segment Reporting Information [Line Items]
Income (loss) from construction operations	(14,510)	(12,941)
Capital expenditures	213	53
Depreciation and amortization	2,335	2,770
Civil
Segment Reporting Information [Line Items]
Revenue	390,795	475,575
Civil | Adverse Legal Ruling Pertaining to Bridge Project in New York
Segment Reporting Information [Line Items]
Adverse arbitration, loss in period	(25,500)
Adverse arbitration, loss in period, after tax	$ (18,300)
Loss contingency, after tax, diluted (in dollars per share)	$ (0.36)
Civil | Unfavorable Adjustment Pertaining to Change in Estimate in Mass Transit Project
Segment Reporting Information [Line Items]
Adverse arbitration, loss in period	$ (17,600)
Adverse arbitration, loss in period, after tax	$ (13,900)
Loss contingency, after tax, diluted (in dollars per share)	$ (0.27)
Civil | Operating Segments
Segment Reporting Information [Line Items]
Revenue	$ 460,742	583,144
Income (loss) from construction operations	(967)	50,105
Capital expenditures	11,175	9,564
Depreciation and amortization	17,000	22,713
Civil | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(69,947)	(107,569)
Building
Segment Reporting Information [Line Items]
Revenue	330,648	407,233
Building | Operating Segments
Segment Reporting Information [Line Items]
Revenue	355,978	457,170
Income (loss) from construction operations	9,464	11,216
Capital expenditures	2	73
Depreciation and amortization	401	432
Building | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(25,330)	(49,937)
Specialty Contractors
Segment Reporting Information [Line Items]
Revenue	230,711	324,787
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Revenue	230,864	324,948
Income (loss) from construction operations	(3,894)	1,324
Capital expenditures	638	145
Depreciation and amortization	502	959
Specialty Contractors | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	$ (153)	$ (161)