Note 10 - Construction Joint Ventures (Details Textual) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Contract with Customer, Liability, Total	$ 95,737				$ 109,011								$ 95,737	$ 109,011
Contract Value of Active Construction Joint Venture Projects	3,400,000												3,400,000
Revenue from Contract with Customer, Including Assessed Tax	885,587	$ 1,112,114	$ 866,092	$ 581,813	836,123	$ 1,070,899	$ 828,313	$ 551,696					3,445,606	3,287,031	$ 2,958,374
Retained Earnings (Accumulated Deficit), Ending Balance	594,353	619,690	579,920	610,302	679,453	738,254	676,572	676,705	$ 579,920	$ 676,572	$ 619,690	$ 738,254	594,353	679,453
Net Income (Loss) Attributable to Parent, Total	(19,380)	$ 45,901	$ (24,242)	(62,470)	(52,676)	$ 67,836	$ 5,866	(20,444)					(60,191)	582	34,116
Unconsolidated Construction Joint Venture Net Income (Loss)				$ (20,384)				$ (6,379)	$ (72,835)	$ (2,883)	$ (93,274)	$ 6,245	(120,632)	(44,689)	(45,856)
Unconsolidated Construction Corporate Joint Venture [Member]
Contract with Customer, Liability, Total	$ 749,400												$ 749,400
Number of Active Joint Venture Projects	9												9
Contract Value of Active Construction Joint Venture Projects	$ 11,500,000												$ 11,500,000
Affirmative Claim Recovery Estimate	116,800				92,400								116,800	92,400
Back Charge Claims	15,900				17,900								15,900	17,900
Retained Earnings (Accumulated Deficit), Ending Balance	76,200				63,300								76,200	63,300
Net Income (Loss) Attributable to Parent, Total													(422,500)	(240,300)	62,200
Unconsolidated Construction Joint Venture Net Income (Loss)													(120,600)	(44,600)	(45,900)
Unconsolidated Construction Corporate Joint Venture [Member] | Minimum [Member]
Contract with Customer, Liability, Total	1,300												1,300
Contract Value of Active Construction Joint Venture Projects	$ 89,200												$ 89,200
Equity Method Investment, Ownership Percentage	20.00%												20.00%
Unconsolidated Construction Corporate Joint Venture [Member] | Maximum [Member]
Contract with Customer, Liability, Total	$ 207,500												$ 207,500
Contract Value of Active Construction Joint Venture Projects	$ 3,800,000												$ 3,800,000
Equity Method Investment, Ownership Percentage	50.00%												50.00%
Unconsolidated Construction Corporate Joint Venture [Member] | Performance Guarantee [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 900,000												$ 900,000
Guarantor Obligations, Current Carrying Value	81,900				$ 88,200								81,900	88,200
Unconsolidated Construction Corporate Joint Venture [Member] | Construction [Member]
Contract with Customer, Liability, Total	2,600,000												2,600,000
Co-venturer [Member] | Performance Guarantee [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,700,000												1,700,000
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Contract with Customer, Liability, Total	$ 521,600												$ 521,600
Number of Active Joint Venture Projects	7												7
Contract Value of Active Construction Joint Venture Projects	$ 1,600,000												$ 1,600,000
Revenue from Contract with Customer, Including Assessed Tax													261,200	243,100	190,300
Net Cash Provided by (Used in) Continuing Operations, Total													(13,100)	85,600	36,900
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Minimum [Member]
Contract with Customer, Liability, Total	200												200
Contract Value of Active Construction Joint Venture Projects	700												$ 700
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage													50.00%
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Contract with Customer, Liability, Total	210,500												$ 210,500
Contract Value of Active Construction Joint Venture Projects	$ 410,500												$ 410,500
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage													65.00%
Line Item Joint Venture [Member]
Number of Active Joint Venture Projects	5												5
Unconsolidated Construction Joint Venture Net Income (Loss)													$ 366,000
Line Item Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Contract with Customer, Liability, Total	$ 166,000												166,000
Contract Value of Active Construction Joint Venture Projects	$ 207,000												207,000
Line Item Joint Venture [Member] | Variable Interest Entity [Member]
Revenue from Contract with Customer, Including Assessed Tax													$ 40,000	$ 4,900	$ 22,900