Consolidated Balance Sheets (Parentheticals) - $ / shares $ / shares in Thousands	Dec. 31, 2020	Dec. 31, 2019
Common Class A [Member]
Class of common stock, par value (in dollars per share)	$ 0	$ 0
Class of common stock, shares authorized (in shares)	10,000,000	10,000,000
Class of common stock, shares issued (in shares)	2,595,087	2,576,837
Treasury shares, issued (in shares)	39,467	37,208
Common Class B [Member]
Class of common stock, par value (in dollars per share)	$ 0	$ 0
Class of common stock, shares authorized (in shares)	2,500,000	2,500,000
Class of common stock, shares issued (in shares)	954,283	954,283
Treasury shares, issued (in shares)	182,435	182,435