Quarterly financial data (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2011	Oct. 31, 2010	Jul. 31, 2010	Apr. 30, 2010	Jan. 31, 2010	Oct. 31, 2011	Oct. 31, 2010	Oct. 31, 2009
Quarterly financial data
Sales	$ 331,018	$ 312,255	$ 318,924	$ 270,962	$ 290,182	$ 279,121	$ 251,659	$ 220,589	$ 1,233,159	$ 1,041,551	$ 819,165
Gross margin	196,459	188,050	197,752	166,171	170,271	165,801	153,867	131,675
Net income	$ 54,675	$ 56,550	$ 65,242	$ 45,897	$ 53,556	$ 55,329	$ 32,431	$ 26,732	$ 222,364	$ 168,048	$ (160,055)
Earnings per share:
Basic	$ 0.82	$ 0.83	$ 0.96	$ 0.67	$ 0.79	$ 0.81	$ 0.48	$ 0.40	$ 3.29	$ 2.49	$ (2.38)
Diluted	$ 0.81	$ 0.82	$ 0.95	$ 0.67	$ 0.78	$ 0.80	$ 0.47	$ 0.39	$ 3.25	$ 2.46	$ (2.38)