Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010
Condensed Balance Sheets [Abstract]
Customer receivables, allowances	$ 8,993	$ 8,475
Common stock, par value	$ 0.1	$ 0.1
Common stock, shares authorized	70,000,000	70,000,000
Common stock, shares outstanding	57,443,324	55,926,945