Note 15 - Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

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

December 31, 201 8	Total		Level 1		Level 2
Assets
Cash equivalents:
Money market funds	$	740	$	38	$	702
Commercial paper		96,759		—		96,759
Investment in marketable securities:
Municipal bonds		6,733		—		6,733
Corporate notes/bonds		146,126		—		146,126
Variable rate demand notes		8,900		—		8,900
Asset-backed securities		32,923		—		32,923
Commercial paper		39,701		—		39,701
Certificate of deposit		956		956		—
	$	332,838	$	994	$	331,844

December 31, 201 7	Total		Level 1		Level 2
Assets
Cash equivalents:
Money market funds	$	3,332	$	31	$	3,301
Municipal bonds		999		—		999
Corporate notes/bonds		2,608		—		2,608
Commercial paper		76,456		—		76,456
Investment in marketable securities:
Municipal bonds		27,657		—		27,657
Corporate notes/bonds		146,401		—		146,401
Variable rate demand notes		3,500		—		3,500
Asset-backed securities		7,185		—		7,185
Commercial paper		56,994		—		56,994
	$	325,132	$	31	$	325,101