Note 11 - Construction Joint Ventures (Details Textual) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Contract with Customer, Liability, Total	$ 159,818	$ 128,443	$ 159,818	$ 128,443	$ 95,737
Contract Value of Active Construction Joint Venture Projects	3,400		3,400
Revenue from Contract with Customer, Including Assessed Tax	915,771	866,092	1,551,698	1,447,905
Retained Earnings (Accumulated Deficit), Ending Balance	520,025	579,920	520,025	579,920	594,353
Net Income (Loss) Attributable to Parent, Total	3,405	(24,242)	(61,965)	(86,712)
Unconsolidated Construction Joint Venture Net Income (Loss)			(30,506)	(72,835)
Unconsolidated Construction Corporate Joint Venture [Member]
Contract with Customer, Liability, Total	$ 618,600		$ 618,600
Number of Active Joint Venture Projects	10		10
Contract Value of Active Construction Joint Venture Projects	$ 11,500		$ 11,500
Affirmative Claim Recovery Estimate	80,900	114,100	80,900	114,100	116,800
Back Charge Claims	18,000	15,100	18,000	15,100	15,900
Retained Earnings (Accumulated Deficit), Ending Balance	77,600	79,900	77,600	79,900	76,200
Net Income (Loss) Attributable to Parent, Total	27,500	(18,900)	(138,500)	(13,700)
Unconsolidated Construction Joint Venture Net Income (Loss)	18,700	52,500	30,500	72,800
Unconsolidated Construction Corporate Joint Venture [Member] | Minimum [Member]
Contract with Customer, Liability, Total	1,200		1,200
Contract Value of Active Construction Joint Venture Projects	$ 12,100		$ 12,100
Equity Method Investment, Ownership Percentage	20.00%		20.00%
Unconsolidated Construction Corporate Joint Venture [Member] | Maximum [Member]
Contract with Customer, Liability, Total	$ 168,200		$ 168,200
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	$ 800		$ 800
Guarantor Obligations, Current Carrying Value	82,300	88,700	82,300	88,700	$ 81,900
Unconsolidated Construction Corporate Joint Venture [Member] | Construction [Member]
Contract with Customer, Liability, Total	2,100,000		2,100,000
Co-venturer [Member] | Performance Guarantee [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,300,000		1,300,000
Consolidated Construction Corporate Joint Venture [Member]
Contract Value of Active Construction Joint Venture Projects	928,500		928,500
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Contract with Customer, Liability, Total	$ 457,500		$ 457,500
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	86,000	76,500	140,700	139,500
Net Cash Provided by (Used in) Continuing Operations, Total			19,800	5,300
Consolidated Construction Corporate Joint Venture [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Minimum [Member]
Contract with Customer, Liability, Total	100		100
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	188,900		$ 188,900
Contract Value of Active Construction Joint Venture Projects	$ 413,800		$ 413,800
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage			65.00%
Line Item Joint Venture [Member]
Number of Active Joint Venture Projects	4		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	$ 133,100		133,100
Contract Value of Active Construction Joint Venture Projects	182,800		182,800
Revenue from Contract with Customer, Including Assessed Tax	$ 18,400	$ 11,800	$ 31,200	$ 12,200