Note 8 - Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

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

	Fair Value Measurements Using
December 31, 2016	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	$	26,335	$	26,335	$	–	$	–
Restricted cash and cash equivalents		5,254		5,254		–		–
Marketable equity securities		138,013		138,013		–		–
Corporate debt securities		71,100		42,323		28,777		–
Asset–backed securities		56,168		–		56,168		–
U.S. Treasury securities		25,181		25,181		–		–
State and municipal securities		31,255		–		31,255		–
Total financial assets	$	353,306	$	237,106	$	116,200	$	–

	Fair Value Measurements Using
December 31, 2015	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	$	38,208	$	38,208	$	–	$	–
Restricted cash and cash equivalents		11,106		11,106		–		–
Marketable equity securities		116,168		116,168		–		–
Corporate debt securities		71,143		32,683		38,460		–
Asset–backed securities		60,910		–		60,910		–
U.S. Treasury securities		21,033		21,033		–		–
State and municipal securities		16,780		–		16,780		–
Total financial assets	$	335,348	$	219,198	$	116,150	$	–