Note 1 - Summary of Significant Accounting Policies 1 (Details Textual) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Oct. 29, 2019 USD ($) $ / shares	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 30, 2019 USD ($)
Revenue, Remaining Performance Obligation, Amount		$ 2,595,085				$ 2,810,827				$ 2,595,085	$ 2,810,827
Revenue from Contract with Customer, Including Assessed Tax		683,196	$ 925,854	$ 834,671	$ 566,332	$ 830,390	$ 955,761	$ 811,866	$ 530,862	3,010,053	3,128,879	$ 2,914,877
Capitalized Computer Software, Additions										12,000	7,400	1,200
Loss Contingency, Estimate of Possible Loss		4,000,000								4,000,000
Loss Contingency Accrual, Payments										66,000
Legal and Accounting Fees										$ 21,600	35,600
Share Price, Potential Dilutive Effect (in dollars per share) | $ / shares										$ 31.47
Warrants Issued With 2.75% Convertible Notes [Member]
Share Price, Potential Dilutive Effect (in dollars per share) | $ / shares	$ 53.44									$ 53.44
Surety Bond [Member]
Loss Contingency, Estimate of Possible Loss		2,300,000								$ 2,300,000
Minimum [Member]
Construction Contracts, Warranty Provisions Period (Month)										6 months
Construction Contracts, Longer Warranty Periods (Year)										2 years
Workers' Compensation Liability		500								$ 500
Maximum [Member]
Construction Contracts, Warranty Provisions Period (Month)										1 year
Construction Contracts, Longer Warranty Periods (Year)										10 years
Workers' Compensation Liability		$ 1,500								$ 1,500
Construction Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)										3 years
Construction Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)										10 years
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)										2 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)										20 years
Software and Software Development Costs [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)										3 years
Software and Software Development Costs [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)										7 years
Caltrans [Member]
Revenue from Contract with Customer, Including Assessed Tax										$ 337,100,000	$ 316,900,000	$ 226,200,000
Caltrans [Member] | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk [Member]
Concentration Risk, Percentage										11.20%	10.10%	7.80%
Virgin Trains USA Florida LLC [Member] | Contract Retention Receivable [Member] | Product Concentration Risk [Member]
Concentration Risk, Percentage										17.20%	13.20%
The 2.75% Convertible Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		2.75%				2.75%				2.75%	2.75%		2.75%
Share Price, Potential Dilutive Effect (in dollars per share) | $ / shares	$ 31.47									$ 31.47
Debt Instrument, Interest Rate, Effective Percentage		6.62%								6.62%
Long-term Debt, Gross		$ 207,400				$ 200,300				$ 207,400	$ 200,300		$ 192,600
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 37,400	22,600				29,700				22,600	29,700		37,400
Debt Instrument, Convertible, Carrying Amount of Equity Component, Tax Amount	$ 9,500												9,500
Debt Instrument, Face Amount													$ 230,000
Increase to Convertible Debt Carrying Value										22,000
Other Current Assets [Member]
Deposit for Legal Settlements		129,000,000								129,000,000
Continuing Operations [Member]
Revenue, Remaining Performance Obligation, Amount		$ 2,600,000				$ 2,800,000				$ 2,600,000	$ 2,800,000
Number of Reporting Units										5
Discontinued Operations [Member]
Number of Reporting Units										2