Note 3 - Supplemental Balance Sheet Information (in Thousands) (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets, Gross, Total	$ 5,021,000	$ 4,970,000
Customer Contracts And Lists [Member]
Finite-Lived Intangible Assets, Gross, Total	2,731,000	2,680,000
Amortization of Intangible Assets, Total	$ 476,000	$ 569,000
Customer Contracts And Lists [Member] \| Minimum [Member]
Finite-Lived Intangible Asset, Useful Life (Year)	5 years
Customer Contracts And Lists [Member] \| Maximum [Member]
Finite-Lived Intangible Asset, Useful Life (Year)	25 years

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration