Note 23 - Impact of Recently Issued Accounting Standards (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 2,825,427,000	$ 2,435,200,000
Cost of Services, Excluding Depreciation, Depletion, and Amortization	$ 1,817,526,000	1,585,865,000
Accounting Standards Update 2014-09 [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total		146,269
Cost of Services, Excluding Depreciation, Depletion, and Amortization		$ 146,269

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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