Note 11 - Construction Joint Ventures (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Contract with Customer, Liability, Total	$ 133,811	$ 104,260	$ 95,737
Contract Value of Active Construction Joint Venture Projects	3,300,000
Revenue from Contract with Customer, Including Assessed Tax	635,927	581,813
Retained Earnings (Accumulated Deficit), Ending Balance	522,639	610,302	594,353
Net Income (Loss) Attributable to Parent, Total	(65,370)	(62,470)
Unconsolidated Construction Joint Venture Net Income (Loss)	(11,816)	(20,384)
Unconsolidated Construction Corporate Joint Venture [Member]
Contract with Customer, Liability, Total	$ 671,400
Number of Active Joint Venture Projects	9
Contract Value of Active Construction Joint Venture Projects	$ 11,400,000
Affirmative Claim Recovery Estimate	117,100	96,200	116,800
Back Charge Claims	18,200	17,900	15,900
Retained Earnings (Accumulated Deficit), Ending Balance	73,200	45,700	$ 76,200
Net Income (Loss) Attributable to Parent, Total	(166,000)	5,200
Unconsolidated Construction Joint Venture Net Income (Loss)	(11,800)	(20,300)
Unconsolidated Construction Corporate Joint Venture [Member] | Minimum [Member]
Contract with Customer, Liability, Total	1,200
Contract Value of Active Construction Joint Venture Projects	$ 11,600
Equity Method Investment, Ownership Percentage	20.00%
Unconsolidated Construction Corporate Joint Venture [Member] | Maximum [Member]
Contract with Customer, Liability, Total	$ 192,200
Contract Value of Active Construction Joint Venture Projects	$ 3,800,000
Equity Method Investment, Ownership Percentage	50.00%
Unconsolidated Construction Corporate Joint Venture [Member] | Performance Guarantee [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 822,400
Guarantor Obligations, Current Carrying Value	81,900	88,200
Unconsolidated Construction Corporate Joint Venture [Member] | Construction [Member]
Contract with Customer, Liability, Total	2,300,000
Co-venturer [Member] | Performance Guarantee [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,500,000
Consolidated Construction Corporate Joint Venture [Member]
Contract Value of Active Construction Joint Venture Projects	919,700
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Contract with Customer, Liability, Total	$ 499,200
Number of Active Joint Venture Projects	7
Contract Value of Active Construction Joint Venture Projects	$ 1,600,000
Revenue from Contract with Customer, Including Assessed Tax	54,700	63,000
Net Cash Provided by (Used in) Continuing Operations, Total	17,100	3,100
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Minimum [Member]
Contract with Customer, Liability, Total	200
Contract Value of Active Construction Joint Venture Projects	$ 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	$ 203,200
Contract Value of Active Construction Joint Venture Projects	$ 410,500
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	65.00%
Line Item Joint Venture [Member]
Number of Active Joint Venture Projects	4
Unconsolidated Construction Joint Venture Net Income (Loss)	$ 327,800
Line Item Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Contract with Customer, Liability, Total	151,000
Contract Value of Active Construction Joint Venture Projects	181,900
Revenue from Contract with Customer, Including Assessed Tax	$ 12,800	$ 400