Note 11 - Deferred Compensation Plans (Details Textual) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Deferred Compensation Arrangement with Individual, Common Stock Reserved for Future Issuance	119,519	116,766
Other Liabilities [Member]
Deferred Compensation Liability, Current and Noncurrent, Total	$ 3.3	$ 3.4

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

No definition available.

Name:	us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant