Stockholders' Deficit (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		1 Months Ended					1 Months Ended		1 Months Ended			3 Months Ended
	Jan. 31, 2013	Oct. 31, 2012	Apr. 30, 2013	Apr. 30, 2012	Sep. 30, 2011 Maximum [Member]	Nov. 30, 2011 Accelerated Share Repurchases Program [Member]	Oct. 31, 2011 Accelerated Share Repurchases Program [Member]	Oct. 31, 2011 October 2011 [Member]	Jan. 31, 2012 October 2011 [Member]	Oct. 31, 2011 October 2011 [Member] Accelerated Share Repurchases Program [Member]	Jan. 31, 2012 November 2011 [Member]	Nov. 30, 2011 November 2011 [Member] Accelerated Share Repurchases Program [Member]	Jan. 31, 2012 Open Market Share Repurchase Program [Member]	Oct. 31, 2011 Open Market Share Repurchase Program [Member]	Apr. 30, 2012 Open Market Share Repurchase Program [Member]	Jan. 31, 2012 Open Market Share Repurchase Program [Member]	Jan. 31, 2013 Common Stock [Member]	Oct. 31, 2012 Common Stock [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues																	763,534	10,666,666
Price per share (in dollars per share)																	$ 18.75	$ 18.75
Proceeds from Issuance of Common Stock	$ 14	$ 192	$ 14	$ 0
Stock Repurchase Program, Authorized Amount					175		100							75
Treasury Stock, Shares, Acquired						2,542,609				2,380,952			1,905,600
Payments for Repurchase of Common Stock			0	75											5	70
Accelerated Share Repurchases, Settlement Payment or Receipt									80		20
Accelerated Share Repurchases, Initial Price Paid Per Share								$ 33.60
Stock Repurchase Program, Remaining Authorized Repurchase Amount							$ 20
Treasury Stock, Additional Shares Acquired												161,657