Note 8 - Investments (Details) (USD $)	9 Months Ended		12 Months Ended					9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2009	Sep. 30, 2013 Called at Par [Member]	Dec. 31, 2009 Downgraded by Moody's [Member]	Sep. 30, 2013 Government Backed Securities [Member]	Sep. 30, 2013 Temporary [Member]	Dec. 31, 2012 Temporary [Member]	Sep. 30, 2013 Other Than Temporary [Member]	Dec. 31, 2012 Other Than Temporary [Member]	Sep. 30, 2013 Auction Rate Securities Backed By Student-Loan Notes [Member]	Sep. 30, 2013 Deferred Compensation Expense [Member]	Dec. 31, 2012 Government Backed Securities [Member]	Sep. 30, 2012 Auction Rate Securities [Member]	Dec. 31, 2012 Auction Rate Securities [Member]	Sep. 30, 2013 Face Value [Member]	Sep. 30, 2013 US Government Agencies Short-term Debt Securities [Member]	Dec. 31, 2012 US Government Agencies Short-term Debt Securities [Member]	Sep. 30, 2013 Government Backed Securities [Member]
Note 8 - Investments (Details) [Line Items]
Auction Rate Securities, Noncurrent	$ 9,847,000		$ 11,755,000		$ 2,000,000	$ 6,300,000										$ 11,800,000	$ 11,800,000			$ 11,800,000
Available-for-sale Securities	113,535,000		113,235,000				91,900,000											91,902,000	85,521,000
Deposits, Money Market Deposits	9,800,000		16,000,000
Available-for-sale Securities, Gross Unrealized Loss	376,000		497,000															3,000	7,000
Available-for-sale Securities, Current														85,500,000
Trading Securities, Change in Unrealized Holding Gain (Loss)			7,000
Other than Temporary Impairment Losses, Investments	(117,000)	(141,000)	520,000					373,000	490,000	30,000	30,000	403,000
Trading Securities, Realized Gain (Loss)				70,000
Investment Income, Interest		40,000
Gain (Loss) on Sale of Securities, Net															40,000
Deferred Compensation Plan Assets	302,000
Deferred Compensation Liability, Current and Noncurrent	311,000
Interest Expense, Other													6,000
Other Cost and Expense, Operating													$ 3,000