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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 |  |

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