Consolidated Statements of Shareholders' Equity (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Class A [Member]
Shares of treasury stock purchased (in shares)	218,344	132,836	21,047
Shares of common stock issued for the exercise of stock option (in shares)	468,318	197,784	52,383
Issuance of restricted common shares, net of forfeitures (in shares)	3,496	19,314	11,565
Dividends declared per common share (in dollars per share)	$ 1.13	$ 0.40	$ 0.34
Settlement of restricted common shares and stock options in connection with recapitalization (in shares)	90,369
Settlement of class B common shares in connection with recapitalization, shares issued (in shares)	3,527,246
Common Class B [Member]
Shares of treasury stock purchased (in shares)	3,677	15,074	7,681
Shares of common stock issued for the exercise of stock option (in shares)	9,296	13,600	35,534
Issuance of restricted common shares, net of forfeitures (in shares)		3,219	1,928
Dividends declared per common share (in dollars per share)	$ 0.60	$ 2.40	$ 2.04
Cash paid settlement of restricted common shares and stock options in connection with recapitalization	$ 3,271
Settlement of class B common shares in connection with recapitalization, shares exchanged (in shares)	3,527,246
Retirement of class B common shares in connection with recapitalization, shares retired (in shares)	4,328,552
Settlement of class B common shares in connection with Recapitalization, cash exchanged	$ 69,099