Stockholders' Equity (Details) (USD $)		12 Months Ended						3 Months Ended			3 Months Ended
	Oct. 31, 2011 contracts	Oct. 31, 2011 Minimum [Member] April 2006 Call Spread Option [Member]	Oct. 31, 2011 Minimum [Member] June 2007 Call Spread Option [Member]	Oct. 31, 2011 Maximum [Member] April 2006 Call Spread Option [Member]	Oct. 31, 2011 Maximum [Member] June 2007 Call Spread Option [Member]	Oct. 31, 2011 0.25% Convertible Senior Notes due May 1, 2013 [Member]	Apr. 10, 2006 0.25% Convertible Senior Notes due May 1, 2013 [Member]	Apr. 30, 2006 0.25% Convertible Senior Notes due May 1, 2013 [Member] April 2006 Call Spread Option [Member]	Oct. 31, 2011 0.875% Convertible Senior Notes due June 15, 2017 [Member]	Jun. 11, 2007 0.875% Convertible Senior Notes due June 15, 2017 [Member]	Jul. 31, 2007 0.875% Convertible Senior Notes due June 15, 2017 [Member] June 2007 Call Spread Option [Member]
Option Indexed to Issuer's Equity [Line Items]
Interest on convertible notes						0.25%	0.25%		0.875%	0.875%
Payment for derivative instrument								$ 28,500,000			$ 42,500,000
Option indexed to issuer's equity, settlement value in cash or net shares		$ 0	$ 0	$ 45,700,000	$ 76,100,000
Number of call spread option contracts held	2