Stockholders' Equity (Narrative) (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended				1 Months Ended
	Oct. 31, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	May 12, 2012	Mar. 31, 2012	May 31, 2012 Series B Preferred Stock [Member]	May 12, 2012 Series B Preferred Stock [Member]	Mar. 31, 2012 Series B Preferred Stock [Member]
Conversion of Stock [Line Items]
Weighted average potential anti-dilutive common shares excluded from the calculation of diluted EPS		0.9	1.5	0.9	0.9
Amount authorized by Board of Directors to repurchase common stock				$ 5,000,000,000
Shares repurchased, shares		4.8		8.3
Shares repurchased, amount		200.0		350.0
Remaining authorized amount in stock repurchase program		500,300,000
Stock repurchase program additional authorized amount	1,000,000,000
Accelerated share repurchase agreement expected contract value	750,000,000
Shares repurchased to satisfy employee tax withholding obligations, shares		0.1		0.5
Repurchases of stock to satisfy employee tax withholding obligations		$ 3,100,000		$ 20,000,000	$ 23,000,000
Conversion rights exercisable by common share holders								One one-thousandth of a series B junior participating preferred share
Preferred stock, par value		$ 0.01		$ 0.01			$ 0.01			$ 0.01
Preferred stock, exercisable price									180
Percentage of market price used to calculate exercise price of rights									50.00%
Class of warrant or right ownership requirement description for exercise of rights						10% or more
Shareholder rights agreement expiration date						May 13, 2013