Note 5 - Stockholders' Equity (Details Textual) - Common Class A [Member] - USD ($) $ / shares in Units, $ in Billions	1 Months Ended	3 Months Ended			6 Months Ended
	Dec. 31, 2012	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2013	Jun. 30, 2015	Jun. 30, 2014	Dec. 11, 2012
Stock Repurchase Program, Authorized Amount							$ 0.1
Common Stock, Dividends, Per Share, Declared	$ 1		$ 0.25	$ 0.25		$ 0.50