Note 4 - Cash, Cash Equivalents and Short-Term Marketable Securities (Details) - Summary of Investments in Marketable Securities (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2013		Mar. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 192,467		$ 195,300
Unrealized Gross Gains	196	[1]	507	[1]
Unrealized Gross Losses	(510)	[1]	(178)	[1]
Fair Value	192,153		195,629
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,820		5,042
Unrealized Gross Gains		[1]		[1]
Unrealized Gross Losses		[1]		[1]
Fair Value	22,820		5,042
US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,081		41,694
Unrealized Gross Gains	6	[1]	27	[1]
Unrealized Gross Losses	(71)	[1]		[1]
Fair Value	41,016		41,721
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,880		2,927
Unrealized Gross Gains		[1]	10	[1]
Unrealized Gross Losses	(8)	[1]	(2)	[1]
Fair Value	2,872		2,935
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	82,822		92,059
Unrealized Gross Gains	95	[1]	215	[1]
Unrealized Gross Losses	(242)	[1]	(45)	[1]
Fair Value	82,675		92,229
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,867		30,932
Unrealized Gross Gains	13	[1]	61	[1]
Unrealized Gross Losses	(104)	[1]	(27)	[1]
Fair Value	27,776		30,966
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,997		22,646
Unrealized Gross Gains	82	[1]	194	[1]
Unrealized Gross Losses	(85)	[1]	(104)	[1]
Fair Value	$ 14,994		$ 22,736

[1] Gross of tax impact