Note 3 - Acquisitions (Details) - Preliminary Allocation of Purchase Price, 2015 - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Note 3 - Acquisitions (Details) - Preliminary Allocation of Purchase Price, 2015 [Line Items]
Goodwill	[1]	$ 508,297	$ 495,679	$ 369,312
2015 Acquisitions [Member]
Note 3 - Acquisitions (Details) - Preliminary Allocation of Purchase Price, 2015 [Line Items]
Equipment and leasehold improvements		1,513
Goodwill		24,296
Net deferred tax liability associated with step-up in book basis		(18)
Assets acquired and liabilities assumed, net		18,931
Total		75,399
Customer Relationships [Member] | 2015 Acquisitions [Member]
Note 3 - Acquisitions (Details) - Preliminary Allocation of Purchase Price, 2015 [Line Items]
Finite-lived intangible assets		28,530
Trade Names [Member] | 2015 Acquisitions [Member]
Note 3 - Acquisitions (Details) - Preliminary Allocation of Purchase Price, 2015 [Line Items]
Finite-lived intangible assets		1,965
Noncompete Agreements [Member] | 2015 Acquisitions [Member]
Note 3 - Acquisitions (Details) - Preliminary Allocation of Purchase Price, 2015 [Line Items]
Finite-lived intangible assets		$ 182

[1] Goodwill recorded in connection with certain tax benefits to be realized in the Company's U.S. income tax returns has been reflected in the United States segment.