Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2011	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stockholders Equity Note [Line Items]
Treasury Stock Acquired, Shares	600,000	7,100,000	7,700,000			16,400,000
Common stock repurchased		$ 200.0				$ 356.0
Shares repurchased cost, Commissions					0.3	0.3
Treasury Stock Acquired in Open Market, Shares					17,700,000
Treasury Stock Acquired in Open Market, Value					419.9
Stock Repurchase Program Remaining Authorized Repurchase Amount					524.7
Treasury Stock Shares Retired		7,700,000
Preferred stock, authorized					25,000,000
Preferred stock, par value					$ 0.10
Preferred stock, issued					0
Outstanding Nonvested stock awards, grant prices range, lower limit					$ 10.59
Outstanding Nonvested stock awards, grant prices range, upper limit					$ 26.31
Outstanding Performance restricted stock units, threshold stock price					$ 26.00
Antidilutive common shares not included in the computation of dilutive earnings per share				3,600,000	2,100,000	3,500,000	7,100,000
Share Repurchase Program Expire In August 2012
Stockholders Equity Note [Line Items]
Authorized repurchase of common stock, value					1,000.0
Share Repurchase Program Expire in May 2011 [Member]
Stockholders Equity Note [Line Items]
Authorized repurchase of common stock, value						$ 500.0
Minimum [Member]
Stockholders Equity Note [Line Items]
Outstanding stock options, exercise prices range, lower limit					$ 11.37
Maximum [Member]
Stockholders Equity Note [Line Items]
Outstanding stock options, exercise prices range, lower limit					$ 26.29