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Note 16 - Concentration of Risk and Enterprise-wide Disclosures - Contract Revenues by Customer (Details) - Customer Concentration Risk [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Caltrans [Member]
Contract Revenues	$ 88,627	$ 96,470		$ 97,637
Caltrans [Member] | Sales Revenue, Net [Member]
Concentration Risk Percentage	12.80%	15.50%		14.50%
TxDOT [Member]
Contract Revenues	$ 85,224	$ 84,129
TxDOT [Member] | Sales Revenue, Net [Member]
Concentration Risk Percentage	12.40%	13.50%
UDOT [Member]
Contract Revenues	$ 79,421		[1]		[1]
UDOT [Member] | Sales Revenue, Net [Member]
Concentration Risk Percentage	11.50%		[1]		[1]
[1] Represents less than 10% of revenues

X

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611

+ Details

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Balance Type:	na
Period Type:	duration

X

- Definition

Costs incurred and are directly related to generating contract revenues.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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Balance Type:	debit
Period Type:	duration

X

- Details

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Namespace Prefix:
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X

- Details

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X

- Details

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X

- Details

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X

- Details

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