Note 6 - Stockholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended			9 Months Ended		26 Months Ended
	Dec. 31, 2012	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013 Common Class A [Member] Related to Tax Withholdings [Member]	Sep. 30, 2013 Common Class A [Member]	Sep. 30, 2013 Common Class A [Member]	Jul. 31, 2012 Common Class A [Member]	Aug. 31, 2011 Common Class A [Member]
Note 6 - Stockholders' Equity (Details) [Line Items]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased								1,000,000	2,000,000
Stock Repurchased During Period, Shares						127,900	1,273,047
Treasury Stock Acquired, Average Cost Per Share (in Dollars per share)					$ 45.04	$ 40.76
Stock Repurchased During Period, Value (in Dollars)						$ 5.2
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		1,726,953
Shares Paid for Tax Withholding for Share Based Compensation						59,721
Adjustments Related to Tax Withholding for Share-based Compensation (in Dollars)						$ 2.7
Common Stock, Dividends, Per Share, Cash Paid (in Dollars per share)	$ 0.10	$ 0.13	$ 0.13	$ 0