Note 4 - Marketable Securities (Details) - Short-Term and Long-Term Marketable Securities (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 105,675	$ 100,362
Unrealized Gains	99	86
Unrealized Losses	(166)	(72)
Fair Value	105,608	100,376
US Government Agencies Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	24,476	21,713
Unrealized Gains	1	2
Unrealized Losses	(63)	(22)
Fair Value	24,414	21,693
Corporate Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	37,314	29,480
Unrealized Gains	30	30
Unrealized Losses	(76)	(20)
Fair Value	37,268	29,490
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,996
Unrealized Losses	(15)
Fair Value	1,981
US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	36,949	44,474
Unrealized Gains	60	49
Unrealized Losses	(10)	(22)
Fair Value	36,999	44,501
Bank Time Deposits [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	4,940	4,695
Unrealized Gains	8	5
Unrealized Losses	(2)	(8)
Fair Value	$ 4,946	$ 4,692