Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Accounts receivables, allowance for doubtful accounts	$ 8,615	$ 8,777
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	32,510,687	32,009,286
Treasury stock, shares	1,284,272	1,260,879