Note 3 - Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

	March 31, 2020
(in thousands)	Total		Level 1		Level 2		Level 3
Assets:
U.S. Government money market funds	$	26,024	$	26,024	$	—	$	—
Tri-party reverse repurchase agreements (collateralized by at least 102% U.S. Treasury and Agency Securities)		123,016		—		123,016		—
Total	$	149,040	$	26,024	$	123,016	$	—

	December 31, 2019
(in thousands)	Total		Level 1		Level 2		Level 3
Assets:
U.S. Government money market funds	$	14,971	$	14,971	$	—	$	—
Tri-party reverse repurchase agreements (collateralized by at least 102% U.S. Treasury and Agency Securities)		154,258		—		154,258		—
Total	$	169,229	$	14,971	$	154,258	$	—