CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 3,837	$ 3,008
Shareholders' equity:
Preferred stock, authorized (in shares)	1,000,000
Preferred stock, issued (in shares)	0
Common stock, par value (in dollars per share)	$ 0.10
Common stock, shares authorized (in shares)	100,000,000
Common stock, shares issued (in shares)	47,002,939	46,751,260
Common stock held in treasury, shares (in shares)	12,053,319	11,479,279