Consolidated Statements of Stockholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock [Member] | Common Class A [Member]
Shares of treasury stock purchased (in shares)	21,047	163,268	65,131
Shares of common stock issued for the exercise of stock options (in shares)	52,383	43,983	140,595
Issuance of restricted common shares, net of forfeitures (in shares)	11,565	73,168	50,038
Dividends declared per common share (in dollars per share)	$ 0.34	$ 0.62	$ 0.06
Common Stock [Member] | Common Class B [Member]
Shares of treasury stock purchased (in shares)	7,681	4,239	4,317
Shares of common stock issued for the exercise of stock options (in shares)	35,534	7,330	23,432
Issuance of restricted common shares, net of forfeitures (in shares)	1,928	12,194	8,340
Dividends declared per common share (in dollars per share)	$ 2.04	$ 3.72	$ 0.36
Common Class A [Member]
Shares of common stock issued for the exercise of stock options (in shares)	52,383
Common Class B [Member]
Shares of common stock issued for the exercise of stock options (in shares)	35,534