Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 7,340	$ 8,673	[1]
Common stock - par value	$ 0.01	$ 0.01	[1]
Common stock - shares authorized	250,000,000	250,000,000	[1]
Common stock - shares issued	107,387,342	105,990,704	[1]
Treasury stock - shares at cost	45,784,146	42,845,444	[1]

[1] Audited