Stockholders' Equity (Narrative) (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended		3 Months Ended		9 Months Ended						1 Months Ended
	Nov. 30, 2012	Oct. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Nov. 23, 2012	May 12, 2012	Mar. 31, 2012	Dec. 31, 2012 Treasury Stock [Member]	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			0.6	4.9	1.2	1.8
Amount authorized by Board of Directors to repurchase common stock					$ 6,000,000,000
Stock repurchase program additional authorized amount		1,000,000,000
Accelerated share repurchase agreement expected contract value	750,000,000
Accelerated share repurchase agreement amount paid	750,000,000
Percentage of shares repurchased	70.00%
Shares of common stock received	13,100,000
Stock repurchase program, period					7 months
Maximum number of shares that could be delivered under the terms of ASR							25.0
Fair value of treasury stock			3,878,600,000		3,878,600,000				3,013,400,000	525,000,000
Additional paid-in capital			1,029,500,000		1,029,500,000				1,179,500,000	225,000,000
Number of shares required to be delivered from unsettled ASR					5.6
Shares repurchased, shares			14.3		22.6
Shares repurchased, amount			575,000,000		925,000,000
Remaining authorized amount in stock repurchase program			700,200,000
Shares repurchased to satisfy employee tax withholding obligations, shares			0.4		0.9
Repurchases of stock to satisfy employee tax withholding obligations			$ 18,100,000		$ 38,100,000	$ 31,700,000
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 11, 2013