Note 6 - Business Combinations (Details Textual) - USD ($)		12 Months Ended
	Nov. 05, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Goodwill		$ 687,404,000	$ 687,778,000	$ 683,683,000
Olson [Member]
Payments to Acquire Businesses, Gross	$ 298,200,000
Amount of Purchase Price in Excess of Fair Value	293,400,000
Goodwill	228,500,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 64,900,000
Goodwill, Purchase Accounting Adjustments		3,400,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment		(7,300,000)
Accrued Expenses, Purchase Accounting Adjustment		(5,900,000)
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred		1,800,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net		$ 298,200,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual			23,000,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual			2,200,000
Business Combination, Acquisition Related Costs			1,600,000
Business Combination, Pro Forma Information, Adjustment Operating Income			$ (2,600,000)
Business Acquisition, Effective Date of Acquisition	Nov. 05, 2014
Olson [Member] | Other Intangible Assets [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	9 years 219 days
Olson [Member] | Customer-Related Intangible Assets [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 60,300,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	10 years 73 days
Olson [Member] | Marketing-Related Intangible Assets [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 4,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	1 year 73 days
Olson [Member] | Technology-Based Intangible Assets [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 600,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 73 days