Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Accounts receivable, allowance	$ 12,505	$ 11,321
Preferred stock undesignated, par value	$ 0.01	$ 0.01
Preferred stock undesignated, shares authorized	1,000	1,000
Preferred stock undesignated, shares issued	0	0
Preferred stock undesignated, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	349,000	349,000
Common stock, shares issued	254,691	250,710
Common stock, shares outstanding	190,382	188,288
Treasury stock, shares	63,951	61,308