Note 6 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

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

			Fair Value Measurements at Reporting Date Using
Description	March 31, 2013		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents
Money market funds	$	51,210	$	51,210	$	-	$	-
Commercial paper		16,997		-		16,997		-
Municipal debt securities		25,113		-		25,113		-
Total cash equivalents		93,320		51,210		42,110		-
Short-term investments
Commercial paper		140,693		-		140,693		-
Municipal debt securities		118,460		-		118,460		-
Corporate debt securities		22,542		-		22,542		-
Government debt securities		3,002		-		3,002		-
Total short-term investments		284,697		-		284,697		-
Long-term investments
Municipal debt securities		10,476		-		10,476		-
Government debt securities		20,012		-		20,012		-
Total long-term investments		30,488		-		30,488		-
Total investment securities	$	408,505	$	51,210	$	357,295	$	-

			Fair Value Measurements at Reporting Date Using
Description	December 31, 2012		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents
Money market funds	$	3,689	$	3,689	$	-	$	-
Commercial paper		370		-		370		-
Municipal debt securities		70,245		-		70,245		-
Total cash equivalents		74,304		3,689		70,615		-
Short-term investments
Certificates of deposit		5,863		-		5,863		-
Commercial paper		81,767		-		81,767		-
Municipal debt securities		106,207		-		106,207		-
Corporate debt securities		33,297		-		33,297		-
Government debt securities		12,005		-		12,005		-
Total short-term investments		239,139		-		239,139		-
Long-term investments
Municipal debt securities		14,022		-		14,022		-
Government debt securities		10,008		-		10,008		-
Total long-term investments		24,030		-		24,030		-
Total investment securities	$	337,473	$	3,689	$	333,784	$	-