Condensed Consolidated Balance Sheets Parenthetical (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts	$ 7,253	$ 6,868
Common, stated value per share	$ 20.00	$ 20.00
Authorized	20,000,000	20,000,000
Issued to voting trustees	13,110,459	12,844,501
Issued to shareholders	2,766,686	2,740,489
In treasury, at cost	(232,282)	(84,566)
Outstanding Common Stock	15,644,863	15,500,424