Note 10 - Construction Joint Ventures (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Contract with Customer, Liability, Revenue Recognized	$ 146,400	$ 95,800
Contract Value of Active Construction Joint Venture Projects	3,400,000
Contract with Customer, Liability, Total	160,149	133,811	$ 171,321
Revenue from Contract with Customer, Including Assessed Tax	669,913	635,927
Retained Earnings (Accumulated Deficit), Ending Balance	352,610	522,639	424,835
Net Income (Loss) Attributable to Parent, Total	(66,195)	(65,370)
Unconsolidated Construction Joint Venture Net Income (Loss)	$ 418	(11,816)
Unconsolidated Construction Corporate Joint Venture [Member]
Number of Active Joint Venture Projects	10
Contract Value of Active Construction Joint Venture Projects	$ 11,600,000
Contract with Customer, Liability, Total	381,000
Affirmative Claim Recovery Estimate	95,400	117,100	88,700
Back Charge Claims	12,900	18,200	13,100
Retained Earnings (Accumulated Deficit), Ending Balance	55,600	73,200	82,500
Net Income (Loss) Attributable to Parent, Total	(16,000)	(166,000)
Unconsolidated Construction Joint Venture Net Income (Loss)	400	(11,800)
Unconsolidated Construction Corporate Joint Venture [Member] | Minimum [Member]
Contract Value of Active Construction Joint Venture Projects	13,400
Contract with Customer, Liability, Total	$ 1,300
Equity Method Investment, Ownership Percentage	20.00%
Unconsolidated Construction Corporate Joint Venture [Member] | Maximum [Member]
Contract Value of Active Construction Joint Venture Projects	$ 3,800,000
Contract with Customer, Liability, Total	$ 87,500
Equity Method Investment, Ownership Percentage	50.00%
Unconsolidated Construction Corporate Joint Venture [Member] | Performance Guarantee [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 500,000
Guarantor Obligations, Current Carrying Value	82,300	81,900	$ 82,300
Unconsolidated Construction Corporate Joint Venture [Member] | Construction [Member]
Contract with Customer, Liability, Revenue Recognized	1,300,000
Co-venturer [Member] | Performance Guarantee [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	800,000
Consolidated Construction Corporate Joint Venture [Member]
Contract Value of Active Construction Joint Venture Projects	$ 1,000,000
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Number of Active Joint Venture Projects	9
Contract Value of Active Construction Joint Venture Projects	$ 1,800,000
Contract with Customer, Liability, Total	414,100
Revenue from Contract with Customer, Including Assessed Tax	82,600	54,700
Net Cash Provided by (Used in) Continuing Operations, Total	13,800	17,100
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Minimum [Member]
Contract Value of Active Construction Joint Venture Projects	2,200
Contract with Customer, Liability, Total	$ 1,200
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 Value of Active Construction Joint Venture Projects	$ 437,400
Contract with Customer, Liability, Total	$ 137,700
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	70.00%
Line Item Joint Venture [Member]
Number of Active Joint Venture Projects			4
Contract Value of Active Construction Joint Venture Projects	$ 187,900
Line Item Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Contract with Customer, Liability, Total	79,500
Revenue from Contract with Customer, Including Assessed Tax	8,600	$ 12,800
Unconsolidated Construction Joint Venture Net Income (Loss)	$ 297,300