Stockholders' Equity (Deficit) (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		1 Months Ended					1 Months Ended		1 Months Ended				3 Months Ended		1 Months Ended		1 Months Ended
	Oct. 31, 2012	Jan. 31, 2013	Jan. 31, 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]	Nov. 30, 2012 Subsequent Event [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]	Oct. 31, 2012 Common Stock [Member]	Jan. 31, 2013 Common Stock [Member]	Nov. 30, 2012 Common Stock [Member] Subsequent Event [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues																	10,666,666		763,534
Price per share (in dollars per share)																		$ 18.75	$ 18.75
Proceeds from Issuance of Common Stock	$ 192	$ 14	$ 0									$ 14
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	70												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