Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Consolidated Balance Sheets [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 5,035	$ 4,317
Preferred Stock, shares authorized	5,000,000	5,000,000
Preferred Stock, shares issued	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	93,218,000	89,783,000
Treasury stock, shares	539,000	533,000