Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Consolidated Balance Sheets
Accounts receivable, allowances for doubtful accounts	$ 4,356	$ 3,258
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	44,450,128	43,748,237
Common stock, shares outstanding	41,352,913	40,673,042
Treasury stock, shares	3,097,215	3,075,195