Note 8 - Fair Value Measurements (Details) - Unrealized Gains And Losses (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Note 8 - Fair Value Measurements (Details) - Unrealized Gains And Losses [Line Items]
Adjusted Cost	$ 115,829,000	$ 113,687,000
Unrealized Gains	35,000	45,000
Unrealized Losses	(541,000)	(497,000)
Total Fair Value	115,323,000	113,235,000
Fair Value Of Investments In Unrealized Position	34,123,000	25,876,000
Money Market Funds [Member]
Note 8 - Fair Value Measurements (Details) - Unrealized Gains And Losses [Line Items]
Adjusted Cost	15,741,000	15,959,000
Unrealized Gains	0
Unrealized Losses		0
Total Fair Value	15,741,000	15,959,000
US Government Agencies Short-term Debt Securities [Member]
Note 8 - Fair Value Measurements (Details) - Unrealized Gains And Losses [Line Items]
Adjusted Cost	87,868,000	85,483,000
Unrealized Gains	35,000	45,000
Unrealized Losses	(19,000)	(7,000)
Total Fair Value	87,884,000	85,521,000
Fair Value Of Investments In Unrealized Position	22,425,000	14,121,000
Auction Rate Preferred Securities [Member]
Note 8 - Fair Value Measurements (Details) - Unrealized Gains And Losses [Line Items]
Adjusted Cost	12,220,000	12,245,000
Unrealized Losses	(522,000)	(490,000)
Total Fair Value	11,698,000	11,755,000
Fair Value Of Investments In Unrealized Position	$ 11,698,000	$ 11,755,000