Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Consolidated Balance Sheets [Abstract]
Accounts receivable, allowances for doubtful accounts	$ 6,843	$ 4,558
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	175,000,000	175,000,000
Common stock, shares issued	46,826,943	45,998,679
Common stock, shares outstanding	43,674,768	42,870,061
Treasury stock, shares	3,152,175	3,128,618