Note 9 - Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Fair Value Measurements Using
December 31, 2019	Fair Value		Quoted Prices in Active Markets For Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and cash equivalents	$	50,334	$	50,334	$	–	$	–
Restricted cash and cash equivalents		10,676		10,676		–		–
Marketable equity securities		152,453		152,453		–		–
Corporate debt securities		65,653		48,584		17,069		–
Asset–backed securities		55,185		–		55,185		–
U.S. Treasury securities		13,410		13,410		–		–
State and municipal securities		13,158		1,975		11,183		–
Total financial assets	$	360,869	$	277,432	$	83,437	$	–

	Fair Value Measurements Using
December 31, 2018	Fair Value		Quoted Prices in Active Markets For Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and cash equivalents	$	43,247	$	43,247	$	–	$	–
Restricted cash and cash equivalents		11,673		11,673		–		–
Marketable equity securities		140,223		140,223		–		–
Corporate debt securities		67,632		47,921		19,711		–
Asset–backed securities		62,068		–		62,068		–
U.S. Treasury securities		21,457		21,457		–		–
State and municipal securities		21,436		–		21,436		–
Total financial assets	$	367,736	$	264,521	$	103,215	$	–