Note 3 - Business Combinations (Details Textual) - USD ($)		3 Months Ended	9 Months Ended
	Nov. 05, 2014	Mar. 31, 2014	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Olson [Member]
Payments to Acquire Businesses, Gross	$ 298,200,000
Goodwill, Period Increase (Decrease)			$ 5,800,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment, Allocation Adjustment			(7,300,000)
Business Combination,Recognized Identifiable Assets Acquired and Liabilities Assumed, Accrued Expenses and Other Liabilities, Allocation Adjustment			(5,900,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Accrued Salaries and Benefits, Allocation Adjustment			200,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities, Allocation Adjustment			2,400,000
Other Payments to Acquire Businesses			1,800,000
Goodwill			230,936,000
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments					$ (1,900,000)
ECA [Member]
Liabilities, Fair Value Disclosure, Recurring		$ 0				$ 2,800,000
Liabilities, Fair Value Adjustment		$ 2,800,000
Goodwill			$ 690,576,000	$ 687,778,000