Note 8 - Fair Value Measurements (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2009
Available-for-sale Securities	$ 81,800,000
Deposits, Money Market Deposits	19,800,000		16,000,000
Available-for-sale Securities, Gross Unrealized Losses	511,000		497,000
Auction Rate Securities, Noncurrent	11,715,000		11,755,000	6,300,000
Trading Securities, Change in Unrealized Holding Gain (Loss)			7,000
Other than Temporary Impairment Losses, Investments	15,000	(90,000)	520,000
Trading Securities, Realized Gain (Loss)				70,000
Investment Income, Interest			40,000
US Government Agencies Short-term Debt Securities [Member]
Available-for-sale Securities, Gross Unrealized Losses	6,000		7,000
Government Backed Securities [Member]
Auction Rate Securities, Noncurrent	11,700,000
Auction Rate Securities Backed By Student-Loan Notes [Member]
Other than Temporary Impairment Losses, Investments	535,000
Temporary [Member]
Other than Temporary Impairment Losses, Investments	505,000		490,000
Other Than Temporary [Member]
Other than Temporary Impairment Losses, Investments	30,000		30,000
Face Value [Member]
Auction Rate Securities, Noncurrent	11,700,000
Government Backed Securities [Member]
Available-for-sale Securities, Current			85,500,000
Auction Rate Securities [Member]
Auction Rate Securities, Noncurrent			$ 11,800,000