Consolidated Balance Sheets (Parentheticals) - $ / shares $ / shares in Thousands	Dec. 31, 2017	Dec. 31, 2016
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	88,788,664	71,229,497
Common stock, shares outstanding (in shares)	83,253,588	66,094,091
Treasury stock (in shares)	5,535,076	5,135,406
Common Class A [Member]
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	15,000,000	15,000,000
Common stock, shares issued (in shares)	8,349,069	8,073,993
Common stock, shares outstanding (in shares)	6,598,377	6,404,862
Treasury stock (in shares)	1,750,692	1,669,131