Note 10 - Financial Instruments and Derivative Financial Instruments:

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents, investments, and trade accounts receivable.  The Company places its cash, cash equivalents, and investments with high credit quality financial institutions, and evaluates the credit worthiness of these financial institutions on a regular basis. Concentrations of credit risk with respect to trade accounts receivable are limited due to the large number of customers comprising the Company's customer base and their geographic dispersion.  At March 31, 2020 and 2019, the Company had no significant concentrations of credit risk.

Letters of Credit

The Company has entered into standby letter of credit agreements with financial institutions relating to the guarantee of future performance on certain contracts.  At March 31, 2020 and 2019, the Company was contingently liable on outstanding standby letters of credit aggregating $13,328 and $8,503, respectively.

Fair Value of Financial Instruments

The estimates of the fair value of financial instruments are summarized as follows:

Cash and cash equivalents:  The carrying amount of cash and cash equivalents approximates fair value due to the short-term maturity of these instruments and are considered Level 1 assets in the fair value hierarchy.

Investments:  The fair value of investments at March 31, 2020 and 2019 approximated the carrying value and are considered Level 2 assets in the fair value hierarchy.