Note 7 - Employee Benefit Plans (Details Textual) - USD ($) $ in Millions	1 Months Ended
	Jul. 31, 2017	Apr. 30, 2017	Jun. 30, 2017
Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer		$ 1.2
Pension Plan [Member] | Subsequent Event [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 5.7
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year			$ 0.4