Note 4 - Investments

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Cash and Cash Equivalents Disclosure [Text Block]

4.

Investments

All of the Company’s investments are classified as available-for-sale and are carried at fair value with unrealized gains and losses recorded as a component of accumulated other comprehensive income (loss), net of related income taxes. The Company held U.S. treasury bills of

$70.0

million at

December 31, 2018.

The Company held certificates of deposit of

$24.0

million at

December 31, 2017.

Unrealized losses and the associated tax impact on the Company’s available-for-sale securities were insignificant as of

December 31, 2018

and

December 31, 2017,

respectively.