CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Thousands	Sep. 30, 2021	Dec. 31, 2020
Stockholders' equity
Capital Stock, par value (in dollars per share)	$ 1	$ 1
Preferred Stock, shares authorized (in shares)	1,000	1,000
Preferred Stock, shares issued (in shares)	0	0
Common Stock [Member]
Stockholders' equity
Common Stock, shares authorized (in shares)	50,000	50,000
Common Stock, shares issued (in shares)	29,906	29,600
Treasury Stock, shares (in shares)	13,374	12,862
Convertible Class A Common Stock [Member]
Stockholders' equity
Common Stock, shares authorized (in shares)	15,000	15,000
Common Stock, shares issued (in shares)	1,810	1,996
Treasury Stock, shares (in shares)	522	522