Note 4 - Current and Non-Current Investments (Details) - Current And Non-Current Investments (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended	9 Months Ended						9 Months Ended	12 Months Ended				9 Months Ended	12 Months Ended	9 Months Ended
	Sep. 30, 2013 US Government and Government Agencies and Authorities [Member] Current [Member]	Dec. 31, 2012 US Government and Government Agencies and Authorities [Member] Non-current [Member]	Sep. 30, 2013 US Government Agencies Debt Securities [Member] Current [Member]	Sep. 30, 2013 US Government Agencies Debt Securities [Member]	Sep. 30, 2013 Certificates of Deposit [Member] Current [Member]	Dec. 31, 2012 Certificates of Deposit [Member] Current [Member]	Dec. 31, 2012 Certificates of Deposit [Member] Non-current [Member]	Sep. 30, 2013 Certificates of Deposit [Member]	Sep. 30, 2013 Corporate Bond Securities [Member] Current [Member]	Dec. 31, 2012 Corporate Bond Securities [Member] Non-current [Member]	Sep. 30, 2013 Variable Rate Demand Obligation [Member] Current [Member]	Dec. 31, 2012 Variable Rate Demand Obligation [Member] Current [Member]	Dec. 31, 2012 Current [Member]	Sep. 30, 2013 Current [Member]	Dec. 31, 2012 Non-current [Member]	Sep. 30, 2013 Non-current [Member]	Dec. 31, 2012 Commercial Paper [Member] Current [Member]	Dec. 31, 2012 Municipal Notes [Member] Current [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 999	$ 10,131	$ 9,069	$ 3,010	$ 1,750	$ 500	$ 3,000	$ 4,250	$ 1,262	$ 1,281	$ 2,175	$ 2,785	$ 6,035	$ 15,255	$ 14,412	$ 7,260	$ 2,499	$ 251
Unrealized Losses		(3)		(1)					(1)	(3)				(1)	(6)	(1)
Fair Value	1,000	10,130	9,077	3,009	1,750	500	3,000	4,250	1,261	1,278	2,175	2,785	6,035	15,263	14,408	7,259	2,499	251
Unrealized Gains	$ 1	$ 2	$ 8											$ 9	$ 2