Note 17 - Employee Benefit Plans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Maximum Defer of Compensation Subject to Statutory Limitations, Percentage	70.00%
Percentage of Employer Matching Contributions Condition, One	100.00%
Percentage of Employee Entitled to Employer Matching Contribution Condition, One	3.00%
Percentage of Employer Matching Contributions Condition, Two	50.00%
Percentage of Employee Entitled to Employer Matching Contribution Condition, Two	2.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 14,900,000	$ 13,100,000	$ 12,300,000
Deferred Compensation Arrangement with Individual, Cash Awards Granted, Percentage	80.00%
Deferred Compensation on Performance Bonuses That Eligible Employee, Percentage	100.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	100.00%
Employee Stock Purchase Plan Shares Authorized	1,000,000
Employee Stock Purchase Plan Annual Maximum Payroll Deduction	$ 25,000
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date	5.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans	24,401
Stock Issued During Period, Value, Employee Stock Purchase Plans, Per Share	$ 44.61
EmployeeStockPurchasePlanNumberOfSharesAvailableForGrant	752,111